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HAYASHI KosukeGraduate School of Engineering / Department of Mechanical EngineeringProfessor
Research activity information
■ Award- Aug. 2023 The Japanese Society for Multiphase Flow, Outstanding Paper Award, 鉛直管におけるフラッディング状態での管内流動特性
- Aug. 2022 The Japanese Society for Multiphase Flow, Outstanding Paper Award, 変形気泡に働くせん断誘起揚力に関する研究
- Oct. 2021 神戸大学工学部, 工学部優秀教育賞
- Mar. 2021 IOP publishing, Outstanding Reviewer Award 2020 (Fluid Dynamics Research)
- Nov. 2020 マツダ財団, マツダ研究助成奨励賞
- Aug. 2017 日本混相流学会, 日本混相流学会「論文賞」, 鉛直管における気液対向流制限Others
- May 2013 15th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-15), Best Poster Award, Void Distribution and Bubble Motion in Bubbly Flows in a 4 X 4 Rod BundleThe “best” poster based on the structure of the presentation (visual quality)International society
- Mar. 2013 日本学術会議IUTAM分科会, 第62回理論応用力学講演会 優秀講演賞, 粘性力及び表面張力の評価法が界面運動の数値予測に及ぼす影響36歳未満の若手研究者による優秀な講演に対して授与されるJapan society
- Jul. 2010 日本混相流学会, 日本混相流学会 奨励賞, 円管内気泡及び液滴の終端上昇速度に関する研究「奨励賞」は、本会会誌または他の学術誌、あるいは本会主催・共催の国際会議論文集に掲載された論文または技術報告（原則として３年以内）を対象とし、際立った独創性、新規性、将来性などが期待され40歳以下の本会会員に贈呈する。International academic award
- Feb. 2006 日本機械学会, 第18回計算力学講演会 学生優秀講演賞, 表面張力評価へのカーン‐ヒリヤード方程式の応用Japan society
- Sep. 2004 日本混相流学会, 日本混相流学会年会講演会2004 学生優秀講演賞, 改良SCAによる流体粒子の界面追跡計算Japan society
- Last, Mar. 2025, International Journal of Multiphase Flow, accepted, EnglishExperimental analysis of velocity field characteristics within bubble wakes in fiber bundle[Refereed]Scientific journal
- Feb. 2025, International Journal of Multiphase Flow, 187, 105173, English[Refereed]Scientific journal
- Last, Elsevier BV, Feb. 2025, Chemical Engineering Research and Design, 215, 274 - 284, English[Refereed]Scientific journal
- Begell House, Feb. 2025, Multiphase Science and Technology, 37(1) (1), 57 - 69, English[Refereed]Scientific journal
- Abstract Experiments on contaminated Taylor flows in a square microchannel were carried out to investigate the effects of surfactant on the bubble shape in the nose and tail regions for different surfactant properties. The nose curvature was found to be proportional to the bubble length at low surfactant concentrations, while it was independent of the concentration at high concentrations. The rate of increase in the nose curvature at the former concentrations can be expressed in terms of the surface coverage ratio. The bubble velocity decreased with increasing the nose curvature, whereas the surface tension reduced by surfactant adsorption worked better to correlate the velocity data. The curvature of the bubble tail increased steeply at low concentrations as a consequence of the early coverage due to interfacial advection. The tail curvature also had a strong correlation with the surface coverage ratio.Springer Science and Business Media LLC, Jan. 2025, Microfluidics and Nanofluidics, 29, #8, EnglishScientific journal
- Dec. 2024, Japanese Journal of Multiphase Flow, 38(4) (4), 404 - 414, Japanese[Refereed]Scientific journal
- Dec. 2024, Japanese Journal of Multiphase Flow, 38(4) (4), 423 - 434, English[Refereed]Scientific journal
- Nov. 2024, 20th Brazilian Congress of Thermal Sciences and Engineering (ENCIT2024), 1 - 8, EnglishVelocity Field External to a Tube Bundle Applying Spatial Filter Velocimetry and Machine Learning[Refereed]International conference proceedings
- Last, Nov. 2024, 20th Brazilian Congress of Thermal Sciences and Engineering (ENCIT2024), 1 - 8, EnglishExperimental Analysis of Velocity Fields within the Bubble Wakes[Refereed]International conference proceedings
- Nov. 2024, The 34th International Symposium on Transport Phenomena, 1 - 5, EnglishExperimental Analysis of Bubble Terminal Velocity in the Presence of Fibers in Aqueous Solutions[Refereed]International conference proceedings
- Corresponding, Nov. 2024, The 34th International Symposium on Transport Phenomena, 1 - 4, EnglishFully-Contaminated State of Single Bubbles in Surfactant-laden Water at Concentrations beyond CMC[Refereed]International conference proceedings
- Nov. 2024, The 34th International Symposium on Transport Phenomena, 1 - 4, EnglishEffects of Surfactant on Shape of Taylor Bubbles in a Square Microchannel[Refereed]International conference proceedings
- Abstract Interface tracking simulations of gas–liquid Taylor flow in horizontal square microchannels were carried out to understand the relation between the pressure drop in the bubble part and the curvatures at the nose and tail of a bubble. Numerical conditions ranged for 0.00159 ≤ CaT ≤ 0.0989, 0.0817 ≤ WeT ≤ 25.4, and 8.33 ≤ ReT ≤ 791, where CaT, WeT, and ReT are the capillary, Weber, and Reynolds numbers based on the total volumetric flux. The dimensionless pressure drop in the bubble part increased with increasing the capillary number and the Weber number. The curvature at the nose of a bubble increased and that at the tail of a bubble decreased as the capillary number increased. The variation of the curvature at the tail of a bubble was more remarkable than that at the nose of a bubble due to the increase in the Weber number, which was the main cause of large pressure drop in the bubble part at the same capillary number. The relation between the bubble velocity and the total volumetric flux was also discussed. The distribution parameter of the drift-flux model without inertial effects showed a simple relation with the capillary number. A correlation of the distribution parameter, which is expressed in terms of the capillary number and the Weber number, was developed and was confirmed to give good predictions of the bubble velocity.Springer Science and Business Media LLC, Jul. 2024, Microfluidics and Nanofluidics, 28(8) (8)[Refereed]Scientific journal
- Elsevier BV, Jul. 2024, Chemical Engineering Science, 120557 - 120557[Refereed]Scientific journal
- Corresponding, Begell House, Jun. 2024, Multiphase Science and Technology, 36(2) (2), 41 - 54, English[Refereed]Scientific journal
- Begell House, Jun. 2024, Multiphase Science and Technology, 36(2) (2), 55 - 73, English[Refereed]Scientific journal
- Corresponding, Elsevier BV, Apr. 2024, Chemical Engineering Research and Design, 204, 343 - 353, English[Refereed]Scientific journal
- BACKGROUND The treatment of vertebrobasilar junction (VBJ) aneurysms is challenging. Although flow diverters (FDs) are a possible treatment option, geometrical conditions hinder intervention. VBJ aneurysms possess dual inflow vessels from the bilateral vertebral arteries (VAs), one of which is ideally occluded prior to FD treatment. However, it remains unclear which VA should be occluded. OBSERVATIONS A 75-year-old male with a growing VBJ complex aneurysm exhibiting invagination toward the brainstem and causing perifocal edema required intervention. Preoperative computational fluid dynamics (CFD) analysis demonstrated that left VA occlusion would result in more stagnant flow and less impingement of flow than right VA occlusion. According to the simulated strategy, surgical clipping of the left VA just proximal to the aneurysm was performed, followed by FD placement from the basilar artery trunk to the right VA. The patient demonstrated tolerance of the VA occlusion, and follow-up computed tomography angiography at 18 months after FD treatment confirmed the disappearance of the aneurysm. LESSONS Preoperative flow dynamics simulations using CFD analysis can reveal an optimal treatment strategy involving a hybrid surgery that combines FD placement and direct surgical occlusion for a VBJ complex aneurysm.Journal of Neurosurgery Publishing Group (JNSPG), Mar. 2024, Journal of Neurosurgery: Case Lessons, 7(10) (10), CASE23736, English[Refereed]Scientific journal
- The Japanese Society for Multiphase Flow, Dec. 2023, JAPANESE JOURNAL OF MULTIPHASE FLOW, 37(4) (4), 401 - 411, Japanese[Refereed]Scientific journal
- The Japanese Society for Multiphase Flow, Dec. 2023, JAPANESE JOURNAL OF MULTIPHASE FLOW, 37(4) (4), 392 - 400, Japanese[Refereed]Scientific journal
- Nov. 2023, 12th International Symposium on Measurement Techniques for Multiphase Flow (ISMTMF 2023), 1 - 3, EnglishEffects of Surfactant on Bubbly Flow in Narrow Rectangular Column[Refereed]International conference proceedings
- Corresponding, Nov. 2023, 12th International Symposium on Measurement Techniques for Multiphase Flow (ISMTMF 2023), 1 - 4, EnglishMeasurements of Surfactant Amount at the Gas-Liquid Interface in Contaminated Taylor Flows in a Microchannel[Refereed]International conference proceedings
- Nov. 2023, 12th International Symposium on Measurement Techniques for Multiphase Flow (ISMTMF 2023), 1 - 3, EnglishDrag Coefficients of Particle-Covered Bubbles Produced Using a Microchannel[Refereed]International conference proceedings
- Elsevier BV, Nov. 2023, Chemical Engineering Research and Design[Refereed]Scientific journal
- Elsevier BV, Oct. 2023, Nuclear Engineering and Design, 412, 112476 - 112476[Refereed]Scientific journal
- Elsevier BV, Sep. 2023, Experimental Thermal and Fluid Science, 147, 110947 - 110947, English[Refereed]Scientific journal
- Corresponding, Elsevier BV, May 2023, Chemical Engineering Research and Design, 193, 75 - 84, English[Refereed]Scientific journal
- Informa UK Limited, Mar. 2023, Heat Transfer Engineering, 1 - 14, English[Refereed][Invited]Scientific journal
- The Japanese Society for Multiphase Flow, Jan. 2023, JAPANESE JOURNAL OF MULTIPHASE FLOW, 37(1) (1), 128 - 137, EnglishScientific journal
- Begell House, 2023, Multiphase Science and Technology, 35(1) (1), 55 - 68, English
Effects of surfactants on lift coefficients, <i>C<sub>L</sub></i>, of single ellipsoidal bubbles rising through linear shear flows were investigated. Two types of surface-active agents, Triton X-100 and 1-octanol, were used. The liquid properties except for the surface tension were identical to those in a clean system of logM = -5.5, where M is the Morton number. The range of the bubble Reynolds number was 0.1 < Re < 70. Bubble shapes were either spherical or ellipsoidal. Comparing with clean bubbles, less deformation of contaminated bubbles was confirmed. A shape correlation without taking the dimensionless shear rate into account gave good evaluations of the bubble aspect ratio, which means that the shear rate is not a dominant factor causing the change of shape deformation. However, drag coefficients were affected by the shear rate. A new correlation of drag coefficients was deduced, which agreed well with the experimental data. Both clean and contaminated <i>C<sub>L</sub></i> data showed a similar tendency: after a drastic decrease in <i>C<sub>L</sub></i>, <i>C<sub>L</sub></i> slightly increases and then decreases to a negative value while increasing the bubble Reynolds number, Re. A difference in concentration of Trion X-100 resulted in only a slight change in <i>C<sub>L</sub></i> at high Re regime. Different types of surfactant resulted in noticeably different values of <i>C<sub>L</sub></i> especially at low Re. The <i>C<sub>L</sub></i> of small bubbles in contaminated systems could be reproduced by a correlation for solid particles, supporting that fully contaminated spherical bubbles behave like solid spheres. For deformed bubbles, <i>C<sub>L</sub></i> can be expressed by relating the negative lift force due to shape deformation with the drag force.
[Refereed]Scientific journal - Begell House, 2023, Multiphase Science and Technology, 35(2) (2), 29 - 41, English[Refereed]Scientific journal
- Elsevier BV, Dec. 2022, Nuclear Engineering and Design, 399, 112001 - 112001, English[Refereed]Scientific journal
- The Japanese Society for Multiphase Flow, Nov. 2022, JAPANESE JOURNAL OF MULTIPHASE FLOW, 36(4) (4), 440 - 451, English[Refereed]Scientific journal
- Nov. 2022, 2022 ANS Winter Meeting and Technology Expo, 1 - 2, EnglishEffects of Upper and Lower Pipe Ends on Interfacial and Wall Friction Factors under Counter-Current Flow Limitation in a Vertical Pipe[Refereed]
- Nov. 2022, 2022 ANS Winter Meeting and Technology Expo, 1 - 2, EnglishEffects of Liquid Viscosity on Friction Factors of Gas-Liquid Swirling Annular Flows in a Vertical Pipe[Refereed]International conference proceedings
- Corresponding, Begell House, Sep. 2022, Multiphase Science and Technology, 34(4) (4), 41 - 55, English[Refereed]Scientific journal
- Begell House, Aug. 2022, Multiphase Science and Technology, 34(4) (4), 1 - 13, English[Refereed]Scientific journal
- Abstract : The authors present the development of the lattice Boltzmann method (LBM) for application to gas-liquid flows, gas mixture, and gas-solid flows. The LBM scheme is constructed using a simple procedure that takes into account collision and propagation processes. The fluid density is calculated using the sum of the distribution function with respect to number of the discrete velocity. Since all distribution functions exist in the computational region with adequate boundary conditions, the LBM is effective for mass conservation and can be adjusted to the multiphase flow simulation. For the multiphase flow simulation, the color-gradient model is first proposed, and then the Shan-Chen and free energy models were implemented using the LBM. Then, the phase-field model, which is commonly used in LBMs, was investigated. The phase-field method easily captures the complicated interface and calculates multiphase flows with high density and viscosity ratios. For multicomponent flows, the LBM can calculate the Stefan--Maxwell equation. The present model calculates multicomponent phenomena, including uphill diffusion, without interpolating the distribution function. For particulate flows, we list the momentum exchange method and the immersed boundary -lattice Boltzmann method (IB-LBM) and explain the occurrence of boundary slip. Finally, we introduce models for wettability, including three phases: gas, liquid, and solid. Keywords : Lattice Boltzmann method, Multiphase flow, Multicomponent flow, Particulate flow, Wettability Cite this article : Seta, T.; Yamamoto, K.; Yoshino, M.; Takada, N.; Matsukuma, Y.; Yamamoto, K.; Hayashi, K.; Kimura, H.; Tomiyama, A. Lattice Boltzmann method for multiphase and multicomponent flows: A review. Muitiph. Sci. Technol. 2022, Vol. 34, in press. https://doi.org/10.1615/MultScienTechn.2022044039Begell House, Jul. 2022, Multiphase Science and Technology, 34, in press., English, International magazine[Refereed]Scientific journal
- Jul. 2022, International Journal of Multiphase Flow, 153, 104134, EnglishFragmentation of Drops Falling through a Miscible Liquid with and without Drop-Drop Interactions[Refereed]Scientific journal
- Elsevier BV, Jun. 2022, World Neurosurgery, 162, 42 - 42, English, International magazine[Refereed]Scientific journal
- May 2022, 2022 Japan-U.S. Seminar on Two-Phase Flow Dynamics, 1 - 6, EnglishEFFECTS OF SWIRL INTENSITY ON INTERFACIAL AND WALL FRICTION FACTORS OF ANNULAR FLOWS IN A VERTICAL PIPE[Refereed]International conference proceedings
- Elsevier BV, May 2022, Computers & Mathematics with Applications, 114, 180 - 187, English[Refereed]Scientific journal
- Begell House, Mar. 2022, Multiphase Science and Technology, English[Refereed]Scientific journal
- Numerical simulations of contaminated spherical drops falling through a stagnant liquid at low Reynolds numbers are carried out using the finite difference method. The numerical results are used to describe the behavior of the surfactant concentrations and to understand the surfactant effects on the fluid motions in detail. The predicted interfacial surfactant concentration, Γ, is almost zero for angles, θ, below a certain value (the stagnant-cap angle, θcap), whereas it steeply increases and reaches a large value for θ>θcap (the stagnant-cap region). The increase in the initial surfactant concentration, C0, in the drop enhances the adsorption from the drop to the interface, which results in the increase in Γ and the decrease in θcap. Peaks appear in the predicted Marangoni stresses around θcap, which causes similar peaks in the pressure distribution. The high-pressure spots prevent the fluid motion along the interface, which results in the formation of the stagnant-cap region and the attenuation of the tangential velocity in the continuous phase. The surfactant flux from the bulk to the interface decreases C in the vicinity of the interface for θ<θcap and the weak diffusion cannot compensate for the reduction in C by adsorption, which results in C at the interface smaller than C0. The pattern of the low C region is determined by the advection and does not smear out because of a small diffusive flux.MDPI AG, Jan. 2022, Fluids, 7(2) (2), 55 - 55, English[Refereed]Scientific journal
- Begell House, Jan. 2022, Multiphase Science and Technology, English[Refereed]Scientific journal
- Elsevier BV, Dec. 2021, Chemical Engineering Science, 245, 116852 - 116852, English[Refereed]Scientific journal
- Oct. 2021, Nuclear Technology, EnglishVoid Fraction and Interfacial Friction in Vertical Circular Pipes with the Square Top End under Flooding Conditions[Refereed]
- The Japanese Society for Multiphase Flow, Sep. 2021, JAPANESE JOURNAL OF MULTIPHASE FLOW, 35(4) (4), 533 - 542, Japanese[Refereed]Scientific journal
- Lattice Boltzmann simulations and a velocity measurement of flows in a cerebral aneurysm reconstructed from MRA (magnetic resonance angiography) images of an actual aneurysm were carried out and the numerical results obtained using the bounce-back schemes were compared with the experimental data to discuss the effects of the numerical treatment of the no-slip boundary condition of the complex boundary shape of the aneurysm on the predictions. The conclusions obtained are as follows: (1) measured data of the velocity in the aneurysm model useful for validation of numerical methods were obtained, (2) the numerical stability of the quadratic interpolated bounce-back scheme (QBB) in the flow simulation of the cerebral aneurysm is lower than those of the half-way bounce-back (HBB) and the linearly interpolated bounce-back (LBB) schemes, (3) the flow structures predicted using HBB and LBB are comparable and agree well with the experimental data, and (4) the fluctuations of the wall shear stress (WSS), i.e., the oscillatory shear index (OSI), can be well predicted even with the jaggy wall representation of HBB, whereas the magnitude of WSS predicted with HBB tends to be smaller than that with LBB.Corresponding, MDPI AG, Sep. 2021, Fluids, 6(10) (10), 338 - 338, English[Refereed]Scientific journal
- Lead, Elsevier BV, Sep. 2021, International Journal of Multiphase Flow, 142, 103653 - 103653, English[Refereed]Scientific journal
- The Japanese Society for Multiphase Flow, Aug. 2021, JAPANESE JOURNAL OF MULTIPHASE FLOW, 35(3) (3), 463 - 472, Japanese[Refereed]Scientific journal
- BACKGROUND: The thin-walled regions (TIWRs) of intracranial aneurysms have a high risk of rupture during surgical manipulation. They have been reported to be predicted by wall shear stress and pressure (PS) based on computational fluid dynamics analysis, although this remains controversial. In this study, we investigated whether the oscillatory shear index (OSI) can predict TIWRs. METHODS: Twenty-five unruptured aneurysms were retrospectively analyzed; the position and orientation of the computational fluid dynamics color maps were adjusted to match the intraoperative micrographs. The red area on the aneurysm wall was defined as TIWR, and if most of the regions on the color map corresponding to TIWR were OSI low (lower quartile range), time-averaged wall shear stress (TAWSS) high, or PS high (upper quartile range), each region was defined as a matched region and divided by the total number of TIWRs to calculate the match rate. In addition, the mean values of OSI, TAWSS, and PS corresponding to TIWRs were quantitatively compared with those in adjacent thick-walled regions. RESULTS: Among 27 TIWRs of 25 aneurysms, 23, 10, and 14 regions had low OSI, high TAWSS, and high PS regions (match rate: 85.2%, 37.0%, and 51.9%), respectively. Receiver operating characteristic curve analysis demonstrated that OSI was the most effective hemodynamic parameter (area under the curve, 0.881), followed by TAWSS (0.798). Multivariate analysis showed that OSI was a significant independent predictor of TIWRs (odds ratio, 18.30 [95% CI, 3.2800-102.00], P < 0.001). CONCLUSIONS: OSI may be a unique predictor for TIWRs. Low OSI strongly corresponds with TIWRs of intracranial aneurysms.Aug. 2021, World neurosurgery, 152, e377-e386, English, International magazineScientific journal
- The Japanese Society for Multiphase Flow, Mar. 2021, JAPANESE JOURNAL OF MULTIPHASE FLOW, 35(1) (1), 85 - 92, Japanese[Refereed][Invited]Scientific journal
- Elsevier BV, Mar. 2021, Nuclear Engineering and Design, 373, 111020 - 111020, English[Refereed]Scientific journal
- Begell House, 2021, Multiphase Science and Technology, 33(3) (3), 17 - 31, English[Refereed]Scientific journal
- Begell House, 2021, Multiphase Science and Technology, 33(3) (3), 53 - 66, English[Refereed]Scientific journal
- Begell House, 2021, Multiphase Science and Technology, 33(4) (4), 1 - 13, English[Refereed]Scientific journal
- Elsevier BV, Jan. 2021, Nuclear Engineering and Design, 371, 110951 - 110951, English[Refereed]Scientific journal
- Wiley, Jan. 2021, Chemie Ingenieur Technik, 93(1-2) (1-2), 247 - 259, English[Refereed][Invited]Scientific journal
- Begell House, 2021, Multiphase Science and Technology, 33(2) (2), 87 - 101, English[Refereed]Scientific journal
- Begell House, 2021, Multiphase Science and Technology, 33(2) (2), 69 - 85, English[Refereed]Scientific journal
- The Japanese Society for Multiphase Flow, Nov. 2020, JAPANESE JOURNAL OF MULTIPHASE FLOW, 35(1) (1), 159 - 167, Japanese[Refereed]Scientific journal
- Elsevier BV, Oct. 2020, International Journal of Multiphase Flow, 131, 103403 - 103403, English[Refereed]Scientific journal
- Lead, Elsevier BV, Aug. 2020, International Journal of Multiphase Flow, 129, 103350 - 103350, English[Refereed]Scientific journal
- Abstract This paper presents an analysis of the performance of the Spatial Filter Velocimetry (SFV) technique applied to external flows across tube bundles to evaluate the benefits of using low particle concentration in a complex geometry. The experimental vector velocity fields were obtained in a tube bundle test section made of acrylic with 20 rows of 4 tubes of 20mm O.D. mounted in a normal triangular configuration and transversal pitch per diameter ratio of 1.25. The SFV results reliability was evaluated by comparing the volumetric flow rates estimated by the experimental vector velocity fields with the volumetric flow rates measured by the flowmeter, showing good agreement. Additionally, the experimental results are used to check the validity of numerical results obtained through CFD simulation. The experiments were conducted for Reynolds numbers of 909, 1842 and 3902. The velocity profiles obtained through the SFV technique agree with the CFD simulations results, which indicate consistent results for both analyzes. Therefore, the numerical and experimental results indicate that the SFV technique provides accurate velocity data and is suitable to be applied to complex geometries, especially in regions away of the test section wall due to the good visibility provided by low particle concentration.American Society of Mechanical Engineers, Jul. 2020, ASME 2020 Fluids Engineering Division Summer Meeting (FEDSM2020), 1 - 12, English[Refereed]International conference proceedings
- Corresponding, Jul. 2020, ASME 2020 Fluids Engineering Division Summer Meeting, EnglishNumerical Simulations of Flows in Cerebral Aneurysms Using the Lattice Boltzmann Method[Refereed]International conference proceedings
- Elsevier BV, Jun. 2020, International Journal of Multiphase Flow, 127, 103270 - 103270, English[Refereed]Scientific journal
- Springer Science and Business Media LLC, Apr. 2020, Flow, Turbulence and Combustion, 105, 1277 - 1301, English[Refereed]Scientific journal
- Springer Science and Business Media LLC, Apr. 2020, Journal of the Brazilian Society of Mechanical Sciences and Engineering, 42(4) (4), English[Refereed]Scientific journal
- Elsevier BV, Mar. 2020, International Journal of Multiphase Flow, 124, 103207 - 103207, English[Refereed]Scientific journal
- Begell House, 2020, Multiphase Science and Technology, 32(4) (4), 325 - 340, English[Refereed]Scientific journal
- Begell House, 2020, Multiphase Science and Technology, 32(3) (3), 221 - 236, English[Refereed]Scientific journal
- Nov. 2019, 11th International Symposium on Measurement Techniques for Multiphase Flow (ISMTMF)Application of Spatiotemporal Filter Velocimetry to Evaluation of Drag Force Acting on Single Drop[Refereed]International conference proceedings
- Nov. 2019, Nuclear Engineering and Design, 353, 110223, English[Refereed]Scientific journal
- Sep. 2019, Multiphase Science and Technology, 31(3) (3), 215 - 234, English[Refereed]Scientific journal
- Jul. 2019, AJK-Fluids, EnglishEvaluation of Drag Force Acting on Single Contaminated Drop based on Velocity Distribution[Refereed]International conference proceedings
- Elsevier BV, Jun. 2019, International Journal of Heat and Mass Transfer, 136, 521 - 530, English[Refereed]Scientific journal
- May 2019, 10th International Conference on Multiphase Flow (ICMF2019), 2 pages, EnglishViscous Stress and Pressure Acting on Interface of Contaminated Drop[Refereed]International conference proceedings
- Corresponding, May 2019, Computers & Mathematics with Applications, 78, 2746 - 2760, English[Refereed]Scientific journal
- May 2019, 10th International Conference on Multiphase Flow (ICMF2019), 2 pages, EnglishEffects of Surfactant on Bubble Breakup at T-Junction and Characteristics of Taylor Flows in Mini and Micro Channels[Refereed]International conference proceedings
- Begell House, May 2019, 10th International Conference on Multiphase Flow (ICMF2019), 33(2) (2), 6 pages - 101, English[Refereed]International conference proceedings
- May 2019, 10th International Conference on Multiphase Flow (ICMF2019), 9 pages, EnglishCombined Effects of Surfactant and Electrolyte on Mass Transfer from Single Carbon-Dioxide Bubbles in Vertical Pipes[Refereed]International conference proceedings
- May 2019, 10th International Conference on Multiphase Flow (ICMF2019), 9 pages, EnglishCharacterization of Velocity Field External to Tube Bundle Using Spatial Filter Velocimetry based on Variable Meshing Scheme[Refereed]International conference proceedings
- Mar. 2019, Multiphase Science and Technology, 31(1) (1), 61 - 71, English[Refereed]Scientific journal
- Feb. 2019, Internation Journal of Multiphase Flow, 111, 285 - 293, English[Refereed]Scientific journal
- Feb. 2019, ISIJ International, 59(2) (2), 209 - 215, English[Refereed]Scientific journal
- OBJECTIVE: Cerebral aneurysm growth often precedes rupture. Definite contributors to aneurysm growth have not been determined even by means of recently developed commercially available computational fluid dynamics (CFD) software. We developed an original CFD tool that can analyze data from time-of-flight magnetic resonance angiography (TOF-MRA) before growth in the growing aneurysms and investigate possible factors for aneurysm growth in the near future. METHODS: We retrospectively reviewed unruptured aneurysms that were treated at our institute because of aneurysm growth (growing group) between April 2013 and March 2017. Stable aneurysms that had demonstrated no growth for more than 5 years were selected (stable group). TOF-MRA data of these aneurysms were retrospectively converted to 3-dimensional vessel geometric data; 3 hemodynamic indices including streamline, wall shear stress (WSS), and oscillatory shear index were calculated by our original CFD tool using the lattice Boltzmann method to quantitatively compare the 2 groups. RESULTS: Six growing aneurysms and 6 stable aneurysms were analyzed. Of the 6 growing aneurysms, WSS on the focal aneurysmal sac increased temporally in the vicinity of the constant low WSS area at the peak systolic phase. By contrast, WSS did not increase during any part of the cardiac cycle in 3 of the 6 stable aneurysms. The peak values of WSS were significantly different between the 2 groups. CONCLUSIONS: A focal increase in WSS in the peak systolic phase may be a risk factor for aneurysm enlargement in the near future.Feb. 2019, World neurosurgery, 122, e1439-e1448 - e1448, English, International magazine[Refereed]Scientific journal
- OBJECTIVE: Thin-walled regions (TIWRs) within cerebral aneurysms have a high risk of rupture during surgical manipulation. Previous reports have demonstrated specific changes in the parameters of computational fluid dynamics in TIWRs; however, they have not been fully evaluated. We identified and investigated a novel parameter, wall shear stress vector cycle variation (WSSVV), with user-friendly software that could predict TIWRs. METHODS: Twelve unruptured cerebral aneurysms were analyzed. TIWRs were defined as reddish areas compared with the normal-colored parent artery on intraoperative views. The position and orientation of these clinical images were adjusted to match the WSSVV color maps. TIWRs and thick-walled regions (TKWRs) were marked and compared with the corresponding regions on WSSVV maps. The default images obtained from WSSVV imaging required appropriate maximum color bar value (MCBV) adjustment for predicting TIWRs. Sensitivity and specificity analyses were performed by changing the MCBV from 300 to 700 at intervals of 100. With the optimal MCBV, the WSSVV values were quantitatively compared. RESULTS: All of the selected 18 TIWRs and 16 TKWRs corresponded to low- and high-value regions of the WSSVV color maps at the adjusted MCBV, respectively. The mean optimal MCBV was 483.3 ± 167.50 (range, 300-700). According to receiver operating characteristic analysis, the best MCBV for predicting TIWRs was 500 (highest sensitivity, 0.89; specificity, 0.94). Under this condition, the quantitative values of the computational fluid dynamics color maps for TIWRs and TKWRs were significantly different (P < 0.01). CONCLUSIONS: Low WSSVV values may indicate TIWRs within cerebral aneurysms.Jan. 2019, World neurosurgery, 121, e287-e295 - e295, English, International magazine[Refereed]Scientific journal
- Elsevier BV, Dec. 2018, International Journal of Heat and Fluid Flow, 74, 28 - 35, English[Refereed]Scientific journal
- Aspect ratios of ellipsoidal bubbles in clean and contaminated systems were measured to investigate the effects of surfactant on the bubble aspect ratio. The bubble diameter ranged from 0.80 to 5.8 mm. Air was used for the gas phase and the glycerol-water solutions were used for the liquid phase. The experimental ranges of the Morton number, M, the bubble Reynolds number, Re, the Eötvös number, Eo, the Weber number, We, and the Tadaki number, Ta, were as follows: 10−7 < M < 10−3, 3.6 × 10−1 < Re < 1.7 × 102, 1.1 × 10−1 < Eo < 5.9, 5.0 × 10−3 < We < 3.7 and 5.3 × 10−2 < Ta < 3.6. Triton X-100 and 1-octanol were used for surfactant. The terminal velocities of bubbles were confirmed to be independent of the surfactant concentration, and therefore, the bubbles were fully-contaminated from the point of view of the terminal velocity. By making use of the aspect ratio data, the applicability of available aspect ratio correlations was examined and an empirical correlation was proposed. The applicability of the proposed correlation was also examined for sodium dodecyl sulphate (SDS) and 1-decanol. As a result, the following conclusions were obtained: (1) the aspect ratio database, which is of use for validating and developing shape correlations, was obtained, (2) the available aspect ratio correlations are not applicable to the present data for fully-contaminated ellipsoidal bubbles, (3) the aspect ratios are well correlated in terms of a combination of the Eötvös and bubble Reynolds numbers, which proves that all the relevant forces, i.e. the viscous, inertial, buoyant and surface tension forces, should be taken into account to correlate bubble shapes, and (4) the empirical correlation of the aspect ratio developed by using the Triton X-100 and 1-octanol data also gives good evaluations for bubbles contaminated with SDS and 1-decanol in spite of largely different adsorption-desorption characteristics.Elsevier Inc., Sep. 2018, Experimental Thermal and Fluid Science, 96, 460 - 469, English[Refereed]Scientific journal
- Elsevier, Sep. 2018, Experimental Thermal and Fluid Science, 96, 397 - 405, EnglishEvaluation of Adsorption of Surfactant at a Moving Interface of a Single Spherical Drop[Refereed]Scientific journal
- Aug. 2018, Nuclear Science and Engineering, 193, 147 - 159, English[Refereed][Invited]Scientific journal
- Jul. 2018, 19th Symposium on Applications of Laser and Imaging Techniques to Fluid Mechanics, Lisbon 2016, EnglishDiagnostics of flow about a contaminated single drop using spatiotemporal filter velocimetry[Refereed]International conference proceedings
- Experiments on air–water two-phase swirling annular flows in a vertical pipe of 40 mm diameter were carried out at atmospheric pressure and room temperature to investigate interfacial and wall friction factors, fi and fw. The friction factors were evaluated using measured pressure drops and void fractions. Measurements of liquid film thickness and flow observation were also conducted. The ranges of the gas and liquid volume fluxes, JG and JL, were 12.5 ≤ JG ≤ 20.0 m/s and 0.03 ≤ JL ≤ 0.11 m/s, respectively. The main conclusions obtained are as follows: (1) fi and fw in swirling annular flows are several times larger than those in non-swirling flows, (2) fi is well correlated in terms of the liquid volume fraction and the gas Reynolds number, ReG, (3) ReG and the liquid Reynolds number, ReL, are required for correlating fw, and (4) the liquid film thicknesses in two-phase swirling flows in a one-fifth model of a BWR separator are well predicted using the two-fluid model and the correlations of fi and fw developed based on the experimental data.Elsevier Ltd, Apr. 2018, Nuclear Engineering and Design, 330, 97 - 105, English[Refereed]Scientific journal
- Apr. 2018, 8th European-Japanese Twp-Phase Flow Group Meeting, EJTPFGM-8, 1, EnglishWall and Interfacial Shear Stress of Swirling Annular Flow[Refereed]International conference proceedings
- Apr. 2018, 8th European-Japanese Twp-Phase Flow Group Meeting, EJTPFGM-8, 1, EnglishNumerical Simulation of a Drop in Contaminated Systems from low concentration to CMC[Refereed]International conference proceedings
- We analytically and numerically investigate the boundary slip, including the velocity slip and the temperature jump, in immersed boundary-thermal lattice Boltzmann methods (IB-TLBMs) with the two-relaxation-time collision operator. We derive the theoretical equation for the relaxation parameters considering the effect of the advection velocity on the temperature jump of the IB-TLBMs. The analytical and numerical solutions demonstrate that the proposed iterative correction methods without the computational cost of the sparse matrix solver reduce the boundary slip and boundary-value deviation as effectively as the implicit correction method for any relaxation time. Because the commonly used multi-direct forcing method does not consider the contributions of the body force to the momentum flux, it cannot completely eliminate the boundary slip because of the numerical instability for a long relaxation time. Both types of proposed iterative correction methods are more numerically stable than the implicit correction method. In simulations of flow past a circular cylinder and of natural convection, the present iterative correction methods yield adequate results without the errors of the velocity slip, the temperature jump, and the boundary-value deviation for any relaxation time parameters and for any number of Lagrangian points per length. The combination of the present methods and the two-relaxation-time collision operator is suitable for simulating fluid flow with thermal convection in the multiblock method in which the relaxation time increases in inverse proportion to the grid size.John Wiley and Sons Ltd, Mar. 2018, International Journal for Numerical Methods in Fluids, 86(7) (7), 454 - 490, English[Refereed]Scientific journal
- A semi-empirical correlation for CCFL (counter-current flow limitation) in vertical pipes was derived from one-dimensional momentum equations. Available correlations such as the empirical correlations proposed by Wallis (1969) and Zapke and Kröger (1996) can be deduced from the derived fundamental functional form of the semi-empirical correlation in limiting flow conditions. Comparisons between the semi-empirical correlation with available experimental data of CCFL taking place at the sharp-edged lower end of a vertical pipe showed that the correlation is applicable for various fluid properties and pipe diameters. The fundamental functional form of the correlation was also transformed so as to express the characteristics of CCFL occurring at the sharp-edged upper end of a vertical pipe. The present fundamental functional form of CCFL correlation is useful not only to express CCFL data but also to understand how relevant parameters play their roles in the CCFL characteristics.Elsevier Ltd, Mar. 2018, Nuclear Engineering and Design, 328, 182 - 187, English[Refereed]Scientific journal
- Feb. 2018, International Journal of Multiphase Flow, 99, 86 - 93, English[Refereed]Scientific journal
- Experiments on aeration from a bubble diffuser pipe having five aeration holes were carried out to in vestigate the effects of the azimuthal angle of the holes and liquid viscosity on flows inside and outside the pipe. The azimuthal angle was varied by rotating the pipe. When the azimuthal angle of the hole exceeded a certain angle, the liquid height inside the pipe was fixed just below the holes at any liquid viscosity, which resulted in preventing of the form ation of liquid slugs inside the pipe. Hence, uniform aeration was realized just by rotating the pipe. The downstream gas flow rates from holes were slightly higher than those upstream, which is due to the pressure recovery in the direction of the stream.Society of Chemical Engineers, Japan, 2018, Kagaku Kogaku Ronbunshu, 44(1) (1), 59 - 66, Japanese[Refereed]Scientific journal
- Mass transfer rates, k(L), of single carbon-dioxide (CO2) bubbles rising through vertical pipes filled with electrolyte aqueous solutions were measured to investigate the effects of the presence of electrolyte on k(L) Sodium chloride (NaCI) was used for electrolyte and its concentration was varied from 3.5 to 14 wt.%. The pipe diameters, D, were 12.5, 18.2 and 25.0 mm and the bubble diameter, d, ranged from 5 to 25 mm. The diameter ratio, lambda(= d/D), was varied from 0.2 to 1.7, to cover various bubble shapes, i.e. ellipsoidal, cap, semi-Taylor bubbles and Taylor bubbles. The conclusions obtained are as follows: (1) k(L) in the NaCI aqueous solutions decreases with increasing the NaCI concentration mainly due to the reduction of the diffusion coefficient of CO2 in the liquid phase, (2) the Sherwood numbers, Sh, of Taylor bubbles of L/D > 1 in the NaCI aqueous solutions can be well evaluated using the available Sherwood number correlation for clean Taylor bubbles, where L is the length of a Taylor bubble, (3) Sh of ellipsoidal, cap, semi-Taylor bubbles and Taylor bubbles of LID <= 1 in the clean water and NaCI aqueous solutions can be well correlated in terms of the Peclet number and the dimensionless bubble diameter d* = d/d(T), where d(T) is the bubble diameter at the transition from the ellipsoidal-cap bubble regime to the semi-Taylor bubble regime, and (4) the Sh correlations give good predictions for long-term bubble dissolution processes in NaCI aqueous solutions. (c) 2017 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2017, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 115, 663 - 671, English[Refereed]Scientific journal
- Spatiotemporal filter velocimetry (SFV) was extended to Lagrangian measurements with boundary-fitted measurement areas, and was applied to flows about single spherical drops of glycerol-water solution falling in stagnant silicon oil under clean and contaminated conditions to examine its applicability to the estimation of the Marangoni stress and surfactant concentration at a moving interface. Effects of bulk concentration of surfactant on the velocity field, the Marangoni stress and the surface concentration of surfactant were discussed from the measured data. As a result, we confirmed that accurate velocity distribution in the vicinity of the interface measured by SFV enables us to evaluate interfacial velocity and interfacial shear stresses and to estimate the Marangoni stress, interfacial tension and surfactant concentration at the interface with the assumption of negligible surface viscosity. The flow inside the drop and the interfacial velocity become weak due to the Marangoni stress caused by the gradient of surfactant concentration at the interface as the bulk concentration of surfactant increases. These results demonstrate that SFV is of great use in experimental analysis of adsorption and desorption kinetics at a moving interface.Elsevier Ltd, Dec. 2017, International Journal of Multiphase Flow, 97, 157 - 167, English[Refereed]Scientific journal
- Dec. 2017, 10th International Symposium on Measurement Techniques for Multiphase Flow (ISMTMF2017), EnglishEvaluation of Adsorption of Surfactant at a Drop Interface using Spatiotemporal Filter Velocimetry[Refereed]International conference proceedings
- Experiments on aeration from a bubble diffuser pipe having five aeration holes are carried out to investigate effects of the azimuthal angle of the holes on flows inside and outside the pipe. The azimuthal angle is varied by rotating the pipe. When the hole angle becomes larger than a certain angle, the liquid height inside the pipe is fixed just below the holes, which results in the prevention of slugging inside the pipe. The effects of hole angle on bubble generation mode and bubble size are small except for the large hole angles, at which generated bubbles are to break up due to an interaction between the bubbles and the pipe wall. Hence uniform aeration is easily realized just by rotating the pipe to some extent. Uniform aeration is also realized with a longer diffuser pipe having ten aeration holes by rotating the pipe. The power in aeration is evaluated from the pressure difference and the total gas inflow. Although the decrease in the hole diameter is also effective to realize the uniform aeration, the increase in the azimuthal angle is superior to the former from the point of view of energy saving.ELSEVIER SCIENCE INC, Dec. 2017, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 89, 90 - 97, English[Refereed]Scientific journal
- Nov. 2017, ANS Winter Meeting and Nuclear Technology Expo, 2 pages, EnglishSpatiotemporal Flow Structure of Counter-Current Two-Phase Annular Flows[Refereed]International conference proceedings
- Lift coefficients, C-L, of single bubbles in linear shear flows are measured to investigate effects of the bubble shape, the liquid velocity gradient and the fluid property on C-L. The range of the Morton number, M, tested is from logM = -6.6 to -3.2. The shapes of bubbles are spherical and ellipsoidal. A correlation of bubble aspect ratio for single bubbles in infinite stagnant liquids proposed in our previous study can give good evaluations for bubbles in the linear shear flows. The C-L of spherical bubbles at low bubble Reynolds numbers, Re, depend on the dimensionless shear rate Sr and Re and decrease with increasing Re. These characteristics agree with the Legendre-Magnaudet correlation. The use of a single dimensionless group such as Re, the Eotvos number, the Weber number and the Capillary number cannot correlate C-L of non-spherical bubbles. The trend of the critical Re for the reversal of the sign of C-L is the same as that for the onset of oscillation of bubble motion, which supports the mechanism proposed by Adoua et al., at least within the range of -6.6 <= logM <= -3.2. An experimental database of C-L is provided for validation of available C-L models and CFD. (C) 2017 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Nov. 2017, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 96, 113 - 122, English[Refereed]Scientific journal
- Prevention of Settlement of Cyprids to the Bottom of a Spherical Surface by Small-Bubbles FlowA round-shaped flask fixed in a fish tank was continuously covered by small bubbles. The number of barnacles grew on the lower hemisphere was 35 to 45 individuals when small bubbles were supplied for 30 days. When bubbles were not supplied, 664 individuals settled on the area. Small bubbles with diameters of 51 to 100 μm showed the highest frequency around the lower hemispherethe Society of Sea Water Science, Japan, Oct. 2017, Bulletin of the Society of Sea Water Science, Japan, 71(5) (5), 315 - 320, Japanese[Refereed]Scientific journal
- The swirler and the 1st pick-off ring (POR) of a gas-liquid separator are improved to reduce the pressure drop, DPT, in the separator while keeping the flow rate of separated liquid, WST, high. Two swirler designs are presented, i.e. V8 (swirler with eight vanes) and V6 (swirler with six vanes), whose diameters of the hubs supporting the vanes are smaller than that of the normal swirler, N8, and the nose shape of vanes are coned. The swirlers are installed into a one-fifth scale separator with three PORs. The gap width of the 1st POR is reduced to the value of the liquid film thickness in the barrel of the separator and the rear shape of the 1st POR is smoothed. The performance of the downscaled separator with the proposed swirlers and the 1st POR are evaluated under the nominal operating condition of the Hyper BWR and a higher quality condition. As a result, the following conclusions are obtained in the present experimental range: (1) DPT in the separator is reduced by 23% using V8, and V8 gives the same WST as N8, confirming that the decrease in the hub diameter and the coned-nose shape of vanes are effective, (2) V6 can realize further reduction of DPT (38%) without deteriorating the liquid-separation rate, (3) the reduced gap width of the 1st POR and a tapered shape of the downstream side of the 1st POR are also effective to decrease the pressure drop, i.e. the improved POR decreases DPT by 42% and 54% by combining with V8 and V6, respectively, and (4) the improved separators also show good performances in DPT and WST at the higher quality condition. (C) 2017 Elsevier B.V. All rights reserved.ELSEVIER SCIENCE SA, Oct. 2017, NUCLEAR ENGINEERING AND DESIGN, 322, 360 - 367, English[Refereed]Scientific journal
- Sep. 2017, 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics(NURETH-17), 14 pages, EnglishOn CCFL in Collider Test Facility: CCFL Results at PWR Hot-Leg Pipe Geometry with 190 mm Diameter[Refereed]International conference proceedings
- THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Jun. 2017, 混相流, 31(1) (1), 37 - 46, Japanese
One-region computations with the annular flow model were done for counter-current flow limitation (CCFL) at the sharp-edged lower end of vertical pipes to evaluate effects of diameters and fluid properties on CCFL characteristics. CCFL characteristics computed with several correlations for interfacial friction factors were compared with CCFL data and the correlation proposed by Bharathan et al. (which is a function of void fraction) was selected. The adjustment factors were obtained to give good agreement between CCFL characteristics computed with the correlation by Bharathan et al. and CCFL data and were correlated with the viscosity ratio of gas and liquid phases and the dimensionless diameter. By using the correlation for interfacial friction factors by Bharathan et al. modified with the viscosity ratio of gas and liquid phases and the dimensionless diameter, effects of diameters and fluid properties on CCFL characteristics were computed.
[Refereed]Scientific journal - THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Jun. 2017, 混相流, 31(2) (2), 152 - 161, Japanese
To evaluate effects of the diameter on countercurrent flow limitation (CCFL) in vertical pipes, in our previous study, we classified CCFL into CCFL-L at the sharp-edged lower end, CCFL-U at the sharp-edged upper end, and CCFL-P inside the vertical pipe with round-edged upper and lower ends, and we found that the characteristic length in the Wallis parameter, w = D(1-β)Lβ (where D and L respectively denote the diameter and the Laplace capillary length), is respectively β = 0, 1 and β ≈ 0.5 for CCFL-L, CCFL-U and CCFL-P. In this study, we evaluated effects of fluid properties on CCFL in vertical pipes by using existing CCFL data. The most effective fluid properties is the liquid viscosity and we selected the viscosity ratio of gas and liquid (μG/μL) as a dimensionless parameter. From effects of μG/μL on the slope m and constant C in the Wallis correlation, we classified three regions of large positive interrelations of m and C with μG/μL for small μL (room-temperature to high-temperature water), small interrelations of m and C with μG/μL for medium μL (low-concentration glycerol water solution), and the large negative interrelation of m with μG/μL for large μL (high-concentration glycerol water solution). We obtained exponent functions of μG/μL for m and C in the case of the small μL (room-temperature to high-temperature water) for CCFL-L and CCFL-U except CCFL-P without high-temperature CCFL data.
[Refereed]Scientific journal - Jun. 2017, 9th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamic (ExHFT-9), 9 pages, EnglishTerminal Velocities of Single Bubble Rising through Stagnant Liquids and Slurry in a Hele-Shaw Cell[Refereed]International conference proceedings
- Jun. 2017, 9th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamic (ExHFT-9), 8 pages, EnglishPressure Drop in Air-Water Two-Phase Flows in Horizontal U-Bends[Refereed]International conference proceedings
- Jun. 2017, 9th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamic (ExHFT-9), 10 pages, EnglishEvaluation of Adsorption of Surfactant at a Moving Interface of a Single Spherical Drop[Refereed]International conference proceedings
- Mass transfer rates, k(L), of single carbon dioxide bubbles contaminated with alcohols in vertical pipes of 12.5, 18.2 and 25.0 mm diameters were measured to investigate effects of the carbon chain length of the alcohols on kL. Four straight-chain alcohols, i.e. 1-pentanol, 1-heptanol, 1-octanol and 1-decanol, were used. A wide range of bubble diameter, d, covered ellipsoidal and Taylor bubbles. Effects of the alcohol concentration, C-sol, on k(L) were also investigated to make clear the values of C-sol corresponding to fully contaminated conditions. As a result, the following conclusions were obtained. (1) The kL of bubbles contaminated with alcohols decrease with increasing C-sol, and they become constant at high C-sol, i.e. bubbles in the latter C-sol ranges are fully-contaminated from the point of view of mass transfer. On the other hand, the rising velocities decrease with increasing C-sol due to the reduction of surface tension even when k(L) are independent of Cob (2) The k(L). of ellipsoidal bubbles fully-contaminated with alcohols decrease with increasing the carbon chain length, whereas the reduction rate of kL becomes smaller and smaller as the carbon chain length increases. The k(L). of fully-contaminated ellipsoidal bubbles can be expressed by accounting for the adsorption constant of alcohol in an available kL correlation. (3) The increase in the carbon chain length also decreases k(L) of fully-contaminated Taylor bubbles, whereas the effect of carbon chain length on k(L), becomes smaller with increasing d. (C) 2017 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, May 2017, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 108(Part B) (Part B), 1991 - 2001, English[Refereed]Scientific journal
- May 2017, Third International Symposium on Multiscale Multiphase Process Engineering (MMPE2017), 6 pages, EnglishEffects of electrolyte on mass transfer from single carbon-dioxide bubbles in vertical pipes[Refereed]International conference proceedings
- Experimental Investigation of Temperature Distribution in Condensing Steam-Air Flow in a Circular TubeExperiments on a steam-air mixture flowing in a vertical tube were carried out to understand a temperature distribution in the tube and to accumulate a database of condensation heat transfer of the steam-air mixture. The condensation tube used was 49.5 mm in diameter and 510 mm long. The ratio of inlet mass fluxes of air and steam was 3:2. They were mixed at a mixing section and flowed into the condensation tube at fully-developed conditions through a straight tube. The water flowing in the outside of the condensation tube cooled the steam-air mixture. The pressure was 0.125 MPa at the inlet of the tube. The experiments were carried out at two different inlet air temperatures and at three different Reynolds numbers. The temperature was measured at 11 points in the radial direction and 7 levels in the vertical direction in the condensation tube. The local heat fluxes were evaluated from temperature distributions measured in the tube wall. Experimental data showed that the heat transfer coefficient h decreased in the flow direction except when flow at the inlet was in the saturated condition. Vierow & Schrock's correlation well evaluated the decrease trend of hc in the flow direction, however, it failed in evaluating dependence of h on the Reynolds number Rem. Siddique's correlation takes the radial distribution of mass fraction of non-condensable gas into account, which well evaluated the dependence of h on Re . This result implies that the hc correlations should take into account axial and radial distributions of the mass fraction of non-condensable gas as well as liquid film thickness. c c c mApr. 2017, 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017), English[Refereed]International conference proceedings
- Experiments on the total gas holdup, alpha(G), in air-water cylindrical bubble columns were carried out to investigate effects of the column diameter, D-H, and the initial liquid height, H-0, on alpha(G). Ranges of D-H and H-0 were 160 <= D-H <= 2000 mm and 400 <= H-0 <= 4000 mm, respectively. The superficial gas velocity, J(G), was varied from 0.025 to 0.35 m/s. The characteristics of gas holdup showed that all the flows in the present experiments were pure heterogeneous. The following conclusions were obtained for alpha(G) in air-water bubble columns: (1) the effects of D-H and H-0 on alpha(G) are negligible when scaling up from small to large bubble columns, provided that alpha(G) in the small columns are obtained for D-H >= 200 mm and Ho 2200 mm. The height-to-diameter ratio is useless in evaluation of the critical height, above which aG does not depend on H-0, (2) for the above ranges of D-H and H-0, Akita-Yoshida's and Koide's correlations can give good evaluations of alpha(G) for a wide range of J(G) by tuning the model constants, (3) for D-H < 200 mm, the decrease in D-H increases the population of large bubbles, which results in the decrease in alpha(G), and (4) for H-0 less than or similar to 2200 mm and D-H >= 200 mm, alpha(G) at a constant J(G) decreases with increasing H-0 and approaches an asymptotic value, and the Froude number using J(G) and H-0 as the characteristic scales well correlates alpha(G) in this regime. (C) 2016 Elsevier Inc. All rights reserved.ELSEVIER SCIENCE INC, Apr. 2017, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 82, 359 - 366, English[Refereed]Scientific journal
- Interfacial Friction Factor for Counter-Current Gas-Liquid Flows in Vertical PipesWe have been experimentally and analytically evaluated countercurrent flow limitation (CCFL), which is defined by the relationship between volumetric fluxes of updraft gas and falling liquid (J and J ) under flooding conditions, in the hot legs, the pressurizer surge line and the heat transfer tubes of a steam generator, and derived Wallis-type CCFL correlations for them. To generalize a prediction method for CCFL in vertical pipes, in this study, we did one-region computations for CCFL inside vertical pipes (CCFL-P) based on the annular flow model with several correlations for the interfacial friction factors and compared the computed results with air-water CCFL data. From the comparison, we selected the correlation proposed by Bharathan et al. (1978), which is a function of the void fraction. Then we obtained adjustment factors for the diameters of D = 18, 25.4, 31.8 and 50.8 mm by fitting the results computed with the correlation by Bharathan et al. (1978) to the air-water CCFL data and derived an adjustment function with the dimensionless diameter (D ). The results showed that the interfacial friction factors should be large for a large diameter pipe. It is difficult, however, to evaluate effects of fluid properties on the interfacial friction factors due to lack of steam-water CCFL data. G L *日本混相流学会, Mar. 2017, 混相流, 31(1) (1), 37 - 46, Japanese[Refereed]Scientific journal
- Lift coefficients, CL, of single bubbles in linear shear flows are measured to investigate effects of the bubble shape, the liquid velocity gradient and the fluid property on CL. The range of the Morton number, M, tested is from logM = − 6.6 to − 3.2. The shapes of bubbles are spherical and ellipsoidal. A correlation of bubble aspect ratio for single bubbles in infinite stagnant liquids proposed in our previous study can give good evaluations for bubbles in the linear shear flows. The CL of spherical bubbles at low bubble Reynolds numbers, Re, depend on the dimensionless shear rate Sr and Re and decrease with increasing Re. These characteristics agree with the Legendre-Magnaudet correlation. The use of a single dimensionless group such as Re, the Eötvös number, the Weber number and the Capillary number cannot correlate CL of non-spherical bubbles. The trend of the critical Re for the reversal of the sign of CL is the same as that for the onset of oscillation of bubble motion, which supports the mechanism proposed by Adoua et al., at least within the range of −6.6 ≤ logM ≤ −3.2. An experimental database of CL is provided for validation of available CL models and CFD.Elsevier Ltd, 2017, International Journal of Multiphase Flow, 96, 113 - 122, English[Refereed]Scientific journal
- THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Dec. 2016, 混相流, 30(4) (4), 392 - 401, Japanese
Characteristics of counter-current flow limitation (CCFL) inside vertical pipes with sharp-edged upper end (CCFL-P/SE) and with round-edged upper and lower ends (CCFL-P) were evaluated to clarify the dependence of the limiting locations. The CCFL is defined by the relationship between the gas and liquid volumetric fluxes (JG and JL) under a quasi-steady state after onset of flooding. CCFL correlations were constructed for CCFL-P/SE and CCFL-P based on the previous experimental data. The correlations were compared to the characteristics of CCFL at the vertical pipes of the sharp-edged upper end (CCFL-U) and the sharp-edged lower end (CCFL-L). CCFL-P has the highest liquid volumetric flux when CCFL occurs, and the lowest is CCFL-L. For the Wallis correlation, selection of the characteristic length of w = D(1-β)Lβ (where D and L respectively denote the diameter and the Laplace capillary length) is quite important. Our results have indicated that CCFL-P/SE and CCFL-P are also expressed by β ≈ 0.5, CCFL-U is expressed by β = 1, and CCFL-L is expressed by β = 0.
[Refereed]Scientific journal - Experiments on air-water two-phase swirling flows in a one-fifth scale model of a steam separator with three pick-off rings (PORs) are carried out to investigate characteristics of two-phase swirling flows and separator performance. In addition to flow observation, liquid film thickness, flow rates of separated liquid and pressure drops are measured. The ranges of the gas and liquid volume fluxes, J(G) and J(L), tested are 12.0 <= J(G) <= 17.8 m/s and 0.05 <= J(L) <= 0.11 m/s, respectively. The main conclusions obtained are as follows: (1) the liquid film thicknesses at the PORs are smaller than the gap widths of the PORs under the nominal operating condition, which results in a high liquid-separation rate, (2) the increase in J(G) decreases the flow rate of unseparated liquid, whereas the flow rate of unseparated liquid is independent of J(L) except for low J(G) conditions, under which the liquid film thicknesses at the 2nd and 3rd PORs tend to be larger than the gap widths of PORs, (3) the presence of the 2nd and 3rd PORs realizes high liquid-separation rates by capturing the liquid unseparated at the 1st POR and the pressure drops at the 2nd and 3rd PORs are much smaller than that at the 1st POR, and (4) the pressure drops at the swirler and the 1st POR, which are the main source of the pressure drop of the separator under the nominal operating condition, increase with J(G), whereas J(L) increases only the latter. (C) 2016 Elsevier B.V. All rights reserved.ELSEVIER SCIENCE SA, Nov. 2016, NUCLEAR ENGINEERING AND DESIGN, 308, 205 - 213, English[Refereed]Scientific journal
- Nov. 2016, ANS Conference 2016 Winter Meeting and Nuclear Technology Expo, 3 pages, EnglishA Semi-Empirical Correlation for Counter-Current Flow Limitation in a Vertical Pipe[Refereed]International conference proceedings
- Total gas holdups alpha(G) in a cylindrical slurry bubble column were measured at various values of the superficial gas velocity J(G), the mean particle volumetric concentration C-S and the initial slurry height H-0 to investigate their effects on alpha(G). The column diameter D-H and height were 200 mm and 2000 mm, respectively. The gas, liquid and solid phases were air, water and hydrophilic silica particles of 100 mu m in mean diameter, respectively. Experimental conditions were 0.025 <= J(G) <= 0.40 m/s, 0 <= C-S <= 0.50 and 1.5 <= H-0* <= 5.0, where H-0* = H-0/D-H. The conclusions obtained are as follows: (1) alpha(G) decreases with increasing H0 and becomes independent of H-0 for H-0* > 4 at low J(G), whereas it depends on H-0 at higher J(G) even for H-0* > 4, (2) the increase in C-S decreases alpha(G) up to C-S similar to 0.40, whereas alpha(G) becomes independent of C-S at larger C-S, and (3) alpha(G) in the slurry bubble column at various C-S, H-0 and J(G) are well correlated in terms of the Froude number Fr-H using H-0 as a characteristic length.SOC CHEMICAL ENG JAPAN, Sep. 2016, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 49(9) (9), 824 - 830, English[Refereed]Scientific journal
- May 2016, 9th International Conference on Multiphase Flow, No. 262, 6 pages, EnglishNumerical Simulation of Surfactant Concentration at an Interface of Single Spherical Drop[Refereed]International conference proceedings
- May 2016, 9th International Conference on Multiphase Flow, No. 245, 6 pages, EnglishMass Transfer from Single Carbon Dioxide Bubbles in Water-Alchol Solutions in a Verical Pipe[Refereed]International conference proceedings
- May 2016, 9th International Conference on Multiphase Flow, No. 262, 6 pages, EnglishExperimental Evaluation of Surfacant Concentration at an Interface of Single Spherical Drop[Refereed]International conference proceedings
- May 2016, 9th International Conference on Multiphase Flow, No. 168, 6 pages, EnglishEffects of Azimuthal Angle of Aeration Holes on Flows inside and outside a Bubble Diffuser Pipe[Refereed]International conference proceedings
- In this study, we measured counter-current flow limitation (CCFL) characteristics in an inverted U-tube (18.4 mm diameter and 1.0 m straight-part length) simulating steam generator (SG) U-tubes under conditions of steam condensation at pressures of 0.1-0.14 MPa. Differential pressure P between the top of the inverted U-tube and the lower tank was measured, and the flow patterns wave estimated by comparing the waveforms of P with those in air-water experiments. As a result, we classified the flow patterns under CCFL conditions into CCFL-P, CCFL-L and CCFL-T. The falling water flow rate under CCFL conditions slightly increased as the pressure increased and the cooling water temperature decreased (subcooling of cooling water increased). In the case of CCFL-L, CCFL characteristics in the inverted U-tube were between those in air-water and saturated steam-water experiments at 0.1 MPa. Furthermore, we derived a Wallis type CCFL correlation and its uncertainty from CCFL data, including previously measured data, i.e., J*(1/2)(G) + 0.88J(L)*(1/2) = 0.76 +/- 0.05.TAYLOR & FRANCIS LTD, Apr. 2016, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 53(4) (4), 486 - 495, English[Refereed]Scientific journal
- Effects of the initial liquid height, H-0, of air-water bubble columns on the total gas holdup, alpha(G), were investigated in this study. Systematic databases of alpha(G) in a rectangular and a cylindrical column of the hydraulic diameter DH of 200 mm were obtained. An image processing method was applied to highspeed video images of the liquid height to obtain accurate gas holdup data. Ranges of the superficial gas velocity, J(G), and the dimensionless liquid height, H-0* (= H-0/D-H), were 0.025 <= J(G) <= 0.40 m/s and 1.5 <= H-0(*) <= 5.0, respectively. The bubbly flows observed in these ranges could be classified into either the heterogeneous bubbly flow consisting of bubbles much smaller than D-H or that with huge bubbles of the column-width scale. The main parameter governing the flow regime transition was J(G). The gradient, d(alpha G)/d(JG), of alpha(G) with respect to J(G) was of use in flow regime identification. The increase in H-0* decreased alpha(G) because a long bubble residence time at a high lit) leads to the increase in the mean bubble diameter due to bubble coalescence. The Froude number using H-0. as a characteristic length well correlates alpha(G) at various H-0 An empirical correlation of alpha(G) in terms of the Froude number was then proposed. Comparing the correlation with the alpha(G) data showed that the correlation can give good evaluations of alpha(G) in the rectangular and cylindrical columns by tuning model parameters. (C) 2015 Elsevier Inc. All rights reserved.ELSEVIER SCIENCE INC, Apr. 2016, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 72, 67 - 74, English[Refereed]Scientific journal
- Aspect ratios E of ellipsoidal bubbles in infinite stagnant clean liquids are measured for log M = -6.6, -5.5, -4.9 and -3.9, where M is the Morton number. An empirical correlation of E applicable to a wide range of the Morton number is proposed by making use of the present data and Sugihara's data at log M = -11 (2007). The aspect ratio in this correlation is expressed in terms of the combination of the Eotvos number and the bubble Reynolds number to account for the effects of the inertial, viscous, buoyant and surface tension forces on E. Terminal velocities of ellipsoidal bubbles are accurately predicted by using the proposed correlation and a drag correlation proposed by Rastello et al. (2011). (C) 2015 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Mar. 2016, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 79, 23 - 30, English[Refereed]Scientific journal
- Dec. 2015, Japanese journal of Multiphase Flow, 29(4) (4), 343 - 350, JapaneseEffects of Liquid-Separation Components on Separation Performance of a Steam Separator[Refereed]Scientific journal
- Nov. 2015, ANS Conference 2015 Winter Meeting and Nuclear Technology Expo, 2 pages, EnglishTwo-Phase Swirling Flow in a Gas-Liquid Separator[Refereed]International conference proceedings
- Mass transfer from single fully contaminated carbon dioxide bubbles rising through vertical pipes was measured to investigate the effects of surfactants. The diameter ratio of the bubble diameter to the pipe diameter was varied to cover various bubble shapes from ellipsoidal to Taylor bubbles. Triton X-100 and 1-octanol served as surfactants. The mass transfer rates, k(L), of contaminated bubbles in the ellipsoidal regime were smaller than those of clean bubbles due to the interface immobilization. The k(L) of Taylor bubbles contaminated with Triton X-100 and 1-octanol showed varying trends because of the difference in the surfactant distributions at the bubble interfaces which strongly depend on the Hatta number. The Sherwood numbers of contaminated bubbles were well correlated by introducing the bubble diameter, at which the bubble shape transits from ellipsoidal to Taylor bubbles.WILEY-V C H VERLAG GMBH, Nov. 2015, CHEMICAL ENGINEERING & TECHNOLOGY, 38(11) (11), 1955 - 1964, English[Refereed][Invited]Scientific journal
- Oct. 2015, 7th European-Japanese Two-Phase Flow Group Meeting, 3 pages, EnglishEvaluation of Interfacial Shear Stress of Single Drop Using Spatiotemporal Filter Velocimetry[Refereed]International conference proceedings
- Effects of liquid viscosity on flows inside and outside a bubble diffuser pipe were investigated in this study. Glycerol-Water solutions and air were used for the liquid and gas phases, respectively. A circular pipe having five aeration holes on the topside and larger opening on the bottom side was placed in a rectangular water tank. The pipe diameter was 20 mm and the hole diameter was 5 mm. The liquid viscosity mu(L) ranged from 1 to 100 mPa s and the total gas flow rate Q(IN) ranged from 3 x 10(-4) to 7 x 10(-4) m(3)/s. The flows inside and outside the pipe were observed using a high-speed video camera and the gas flow rates from each aeration hole were measured by capturing bubbles generated from each hole. The liquid entered into the pipe through the aeration hole and the opening, resulting in wavy flow pattern with intermittent slugging. The conclusiohs obtained are as follows: (1) the increases in Q(IN) and mu(L) decrease the frequency of slugging disturbing aeration, so that the gas flow rate from each hole becomes uniform at high Q(IN) and mu(L), (2) the main triggers of slugging are interfacial waves at low mu(L) and interface deformation caused by liquid drops falling from the aeration holes into the pipe at high mu(L), (3) a slugging criterion for inviscid fluids proposed by Mishima and Ishii (1980) is applicable not only to low mu(L) liquids but also to high mu(L) liquids because the wave growth rate is much larger than the viscous damping rate even at high viscosities tested in the present experiments, and (4) the Davidson-Schuler correlation (Davidson and Schuler, 1960) gives reasonable estimations of the bubble diameter not only for low viscosity liquids but also for high viscosity liquids, provided that the influence of slugging is small. (C) 2015 Elsevier Inc. All rights reserved.ELSEVIER SCIENCE INC, Sep. 2015, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 66, 197 - 205, English[Refereed]Scientific journal
- Sep. 2015, 9th International Symposium on Measurement Techniques for Multiphase Flow, 2 pages, EnglishEffects of Liquid Height on Gas Holdup in a Rectangular Bubble Column[Refereed]International conference proceedings
- Jul. 2015, ASME-JSME-KSME Joint Fluids Engineering Conference 2015 (AJK2015-FED), AJK2015 - 21048, 2 pages, EnglishMotion of Contaminated Drops Falling onto Flat Plate[Refereed]International conference proceedings
- The purpose of this study is to derive a counter-current flow limitation (CCFL) correlation and evaluate its uncertainty for steam generator (SG) U-tubes in a pressurized water reactor (PWR). Experiments were conducted to evaluate effects of the liquid viscosity on CCFL characteristics using air-40wt% or air-60wt% glycerol water solution and saturated steam-water at atmospheric pressure with vertical pipes simulating the lower part of the SG U-tubes. The steam-water experiments confirmed that CCFL characteristics could be expressed in terms of the Wallis parameters (J(G)* and J(L)*) for the pipe diameters of D = 14, 20, and 27mm. A CCFL correlation was derived using the ratio mu(G)/mu(L) of the viscosities of the gas and liquid phases, mu(G) and mu(L), as a correction term representing effects of fluid properties, where J(G)(*1/2)(mu(G)/mu(L))(-0.07) was expressed by a cubic function of J(L)(*1/2)(mu(G)/mu(L))(0.1). In the correlation, the constant C indicating the value of J(G)(*1/2)(mu(G)/mu(L))(-0.07) at J(L)* = 0 was (1.04 +/- 0.05), and this uncertainty of +/- 0.05 would cover most of the previous experimental data including the ROSA-IV/LSTF data at 1, 3, and 7 MPa.TAYLOR & FRANCIS LTD, Jun. 2015, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 52(6) (6), 887 - 896, English[Refereed]Scientific journal
- Implicit Temperature-Correction-based Immersed-Boundary Thermal Lattice-Boltzmann Method with Two Relaxation TimesIn the present paper, we verify the effectiveness of the two-relaxation-time (TRT) collision operator in reducing boundary slip of temperature computed by the immersed boundary-thermal lattice Boltzmann method (IB-TLBM). In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part. The Chapman-Enskog expansion indicates that one relaxation time for the antisymmetric component is related to the thermal conductivity. We derive the theoretical relation between a temperature slip at the boundary and reveal that the relaxation time for the symmetric part controls the temperature at the boundary and boundary slip of temperature computed by the IB-TLBM. We apply the IB-TLBM based on the implicit correction method with two relaxation times for the natural convection in a square enclosure containing a circular cylinder. The streamline, isotherms, and average Nusselt number calculated by the proposed method agree well with those of previous numerical studies.The Japan Society of Mechanical Engineers, May 2015, 23th International Conference on Nuclear Engineering (ICONE23), 2015(23) (23), 10 pages, ICONE23 - 1039, English[Refereed]International conference proceedings
- Mass transfer from single carbon dioxide bubbles rising through contaminated water in a vertical pipe of 12.5 mm diameter was measured to investigate effects of surfactant. The bubble diameter was widely varied to cover various bubble shapes such as spheroidal, wobbling, cap and Taylor bubbles. The gas and liquid phases were 99.9% purity carbon dioxide and a surfactant solution made of purified water and Triton X-100. Comparison of mass transfer rates between contaminated and clean bubbles made clear that the surfactant decreases the mass transfer rates of small bubbles. The Sherwood numbers of small bubbles in the extreme cases, i.e. zero and the highest surfactant concentrations, are well correlated in terms of the bubble Reynolds number, Schmidt number and the ratio, 2, of the bubble diameter to pipe diameter. The Sherwood numbers at intermediate surfactant concentrations, however, are not well correlated using available correlations. The mass transfer rates of Taylor bubbles also decrease with increasing the surfactant concentration. They however increase with the diameter ratio and approach those of clean Taylor bubbles as 2 increases. The main cause of this tendency was revealed by interface tracking simulations, i.e. the surfactant adsorbs only in the bubble tail region and the nose-to-side region is almost clean at high A. (C) 2014 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2015, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 83, 652 - 658, English[Refereed]Scientific journal
- The time, t(C), elapsed from bubble contact to the rupture of the liquid film between two bubbles in a quasi two-dimensional column was measured to investigate the effects of the particle diameter on bubble coalescence. The particle diameter ranged from 60 to 150 mu m and the particle volumetric concentration ranged from 0 to 0.50 (50%). The effects of particle diameter on bubble coalescence were evaluated through the experiments and were implemented into a bubble lcoalescence model for a multi-fluid model. Distributions of the gas holdup in a three-dimensional slurry bubble column were also measured using an electrical conductivity probe to obtain experimental data for validation of the coalescence model. The conclusions obtained are as follows: (1) t(C) decreases, in other words, bubble coalescence is enhanced with decreasing the particle diameter, which results in the reduction of the gas holdup of the slurry bubble column, (2) the particle-effect multiplier to t(C) is of great use to take into account the effects of the particle concentration and diameter in multi-fluid simulations of slurry bubble columns, and (3) the interaction between the bubble interfaces and particles in the bubble coalescence process after bubble contact is a local phenomenon and rarely depends on the macroscopic behavior of the interface, which allows us to develop a correlation for particle-induced enhancement of bubble coalescence for three-dimensional bubble columns even with a small experimental setup like a Hele-Shaw cell.SOC CHEMICAL ENG JAPAN, Mar. 2015, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 48(3) (3), 181 - 189, English[Refereed]Scientific journal
- Effects of numerical treatments for the surface tension evaluation on predictions of the motions of droplets ranging from micron to sub-micron meters were investigated. Various combinations of schemes for evaluating the normal to the interface and interface curvature were examined, i.e. the ALE (arbitrary Lagrangian-Eulerian) like scheme and BFA (balanced-force algorithm) for the normal vector and CSF (continuum surface force) and HF (height function) for the interface curvature. The interface motion was predicted using THAINC (tangent of hyperbola with adaptive slope for interface capturing) proposed in our previous study. Numerical errors in pressure and velocity were examined for neutrally buoyant drops of 1 mm in radius to validate the code, which confirmed that the results were similar to those reported in literature: the combination of BFA and HF gave the lowest errors. The droplet size was reduced to 0.1 μm to investigate the accuracy of the schemes for droplet sizes found in industrial coating processes. The static contact angle was then taken into account in the code. The effect of implementation on the errors was examined. The reduction of droplet sizes and implementation of contact angle had no substantial effect on the order of errors. A model for the dynamic contact angle was also implemented and the wetting behaviour of a drop of 1.14 mm in radius was well predicted. Finally a simulation of the wetting behaviour of a sub-micron meter droplet demonstrated that the present code combining BFA, HF and the dynamic contact angle model is accurate in predicting the motion of sub-micron meter droplets.Multi-Science Publishing Co. Ltd, Mar. 2015, Journal of Computational Multiphase Flows, 7(1) (1), 15 - 32, English[Refereed]Scientific journal
- Sound generated by vapor bubbles condensing in subcooled water was measured to investigate effects of the degree, ΔT, of subcooling. Saturated steam from a boiler was injected into a horizontal water pipe flow through an orifice of 1 mm in diameter. The duct diameter was 16 mm and the Reynolds number of water was about 5 × 104. The subcooling was varied from 10 to 40 K. The sound level increased with increasing ΔT for ΔT ≤ 20 K, whereas it was independent of ΔT at higher ΔT. Video images of condensing bubbles revealed that the interfacial velocity of a condensing bubble had the same trend as that of the sound level, and therefore, the interfacial velocity in condensation is the key in the sound level. The rapid condensation at high ΔT induced emission of microbubbles and secondary pressure pulse generation. The latter also contributes to the increase in the sound level.Begell House Inc., 2015, Multiphase Science and Technology, 27(1) (1), 67 - 75, English[Refereed]Scientific journal
- Multi-fluid simulations of heterogeneous bubbly flows in an air-water bubble column were carried out to verify the speculation that a heterogeneous bubbly flow is predictable without turbulence models such as k-epsilon and LES models, provided that the velocity fluctuation caused by large-scale vortical flow structures prevails over the bubble-induced and shear-induced turbulences. Experiments on the heterogeneous air-water bubbly flows in a rectangular bubble column were also carried out to obtain experimental data of the mean velocity, fluctuation velocity and void fraction for validation of the numerical method. A small LDV probe developed in our previous study was utilized to measure the liquid velocity in the column at high spatial and high temporal resolutions. The distribution of void fraction was measured using an electrical conductivity probe. The conclusions obtained under the present experimental conditions are as follows: (1) the small LDV probe is of great use in measuring the distributions of mean and fluctuation velocities of the liquid phase at high spatial and high temporal resolutions, (2) the velocity fluctuation in the heterogeneous regime in the bubble column is mainly due to large-scale vortical structures, and (3) the multi-fluid model can give good predictions of a heterogeneous bubbly flow without using the turbulence models, provided that large-scale vortical structures in the flow prevail over the bubble-induced and shear-induced turbulences. (C) 2014 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2014, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 67, 111 - 121, English[Refereed]Scientific journal
- Nov. 2014, ANS Conference 2014 Winter Meeting and Nuclear Technology Expo, CD-ROM, 2 pages, EnglishCCFL of Steam-Condensate Two-Phase Flow in a U-Tube[Refereed]International conference proceedings
- Sep. 2014, Proc. 2nd International Symposium on Multiscale Multiphase Process Engineering, pp. 94 - 99, EnglishEffects of Surfactant on Mass Transfer from Single Carbon Dioxide Bubbles in Vertical Pipes[Refereed]International conference proceedings
- Sep. 2014, Proc. 2nd International Symposium on Multiscale Multiphase Process Engineering, pp. 230 - 235, EnglishEffects of Height-To-Diameter Ratio on Gas Holdup in a Slurry Bubble Column[Refereed]International conference proceedings
- Sep. 2014, Proc. 2nd International Symposium on Multiscale Multiphase Process Engineering, pp. 106 - 115, EnglishAn Interface Capturing Scheme for Free-Surface Flows in a Flow Channel Consisting of Solid Obstacles[Refereed]International conference proceedings
- Aug. 2014, Proc. 15th International Heat Transfer Conference, IHTC-15, IHTC15 - 08960, 11 pages, EnglishBubble Growth in Microgravity under the Action of Electric Forces: Experiments and Numerical Simulation[Refereed]International conference proceedings
- Jul. 2014, International Conference on Numerical Methods for Multiphase Flow 2014, ICNMMF2014, 2 pages, EnglishNumerical Simulations of Clean and Contaminated Bubbles in Linear Shear Flows[Refereed]International conference proceedings
- Jul. 2014, 17th International Symposium on Applications of Laser Techniques to Fluid Mechamics (LISBON 2014), EnglishEvaluation of Interfacial Shear Stress of Single Drop using Spatiotemporal Filter Velocimetry[Refereed]International conference proceedings
- Effects of numerical treatment of viscous and surface tension forces on predicted motion of an interface are investigated. The viscous force and tangential surface tension force (Marangoni force) are treated in two different ways: one is a smeared-out interface method and the other is a ghost fluid method. In the smeared-out interface method, the arithmetic mean and harmonic mean are tested for evaluation of the viscous stress. Linear shear flows, single oscillating drops and surface tension waves are simulated using these methods. These benchmark tests show that the ghost fluid method gives the most accurate evaluations of the viscous and the Marangoni forces. The harmonic mean can give good evaluations of the tangential viscous stress at clean interface, whereas large errors in the viscous stress are caused for contaminated interface. Although the arithmetic mean causes some errors for clean and contaminated interfaces compared to the ghost fluid method, the error can be reduced by increasing spatial resolution and this method can give more reasonable predictions for contaminated interface than the harmonic mean. The arithmetic mean is therefore recommended rather than the harmonic mean when using the smeared-out interface method.Multi-Science Publishing Co. Ltd, Jun. 2014, Journal of Computational Multiphase Flows, 6(2) (2), 111 - 126, English[Refereed]Scientific journal
- Lead, Feb. 2014, Journal of Nuclear Science and Technology, 51(5) (5), 580 - 589, EnglishVoid distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part II: numerical simulation[Refereed]Scientific journal
- Lack of local void fraction data in a rod bundle makes it difficult to validate a numerical method for predicting gas-liquid two-phase flow in the bundle. Distributions of local void fraction and bubble velocity in each subchannel in a 4x4 rod bundle were, therefore, measured using a double-sensor conductivity probe. Liquid velocity in the subchannel was also measured using laser Doppler velocimetry (LDV) to obtain relative velocity between bubbles and the liquid phase. The size and pitch of rods were 10 and 12.5mm, respectively. Air and water at atmospheric pressure and room temperature were used for the gas and liquid phases, respectively. The volume fluxes of gas and liquid phases ranged from 0.06 to 0.15m/s and from 0.9 to 1.5m/s, respectively. Experimental results showed that the distributions of void fraction in inner and side subchannels depend not only on lift force acting on bubbles but also on geometrical constraints on bubble dynamics, i.e. the effects of rod walls on bubble shape and rise velocity. The relative velocity between bubbles and the liquid phase in the subchannel forms a non-uniform distribution over the cross-section, and the relative velocity becomes smaller as bubbles approach the wall due to the wall effects.TAYLOR & FRANCIS LTD, Feb. 2014, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 51(2) (2), 220 - 230, English[Refereed]Scientific journal
- In the present paper, we verify the effectiveness of the two-relaxation-time (TRT) collision operator in reducing boundary slip computed by the immersed boundary-lattice Boltzmann method (IB-LBM). In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part. The Chapman-Enskog expansion indicates that one relaxation time for the symmetric component is related to the kinematic viscosity. Rigorous analysis of the symmetric shear flows reveals that the relaxation time for the antisymmetric part controls the velocity gradient, the boundary velocity, and the boundary slip velocity computed by the IB-LBM. Simulation of the symmetric shear flows, the symmetric Poiseuille flows, and the cylindrical Couette flows indicates that the profiles of the numerical velocity calculated by the TRT collision operator under the IB-LBM framework exactly agree with those of the multirelaxation time (MRT). The TRT is as effective in removing the boundary slip as the MRT. We demonstrate analytically and numerically that the error of the boundary velocity is caused by the smoothing technique using the delta function used in the interpolation method. In the simulation of the flow past a circular cylinder, the IB-LBM based on the implicit correction method with the TRT succeeds in preventing the flow penetration through the solid surface as well as unphysical velocity distortion. The drag coefficient, the wake length, and the separation points calculated by the present IB-LBM agree well with previous studies at Re = 10, 20, and 40.AMER PHYSICAL SOC, Feb. 2014, PHYSICAL REVIEW E, 89(2) (2), 023307, English[Refereed]Scientific journal
- Interface tracking simulations of mass transfer from Taylor bubbles were carried out to investigate effects of shape oscillation on the mass transfer. Mass transfer from carbon dioxide Taylor bubbles in a glycerol-water solution was also measured to obtain experimental data for the validation of the numerical method. A high spatial resolution was used to resolve thin concentration boundary layers on the bubble interface, which enabled us to capture the agitation of boundary layer due to interfacial waves. The predicted mass transfer coefficients were in good agreements with the experimental data, provided that the spatial resolution was high enough to capture thin concentration boundary layers of high Schmidt number Taylor bubbles. The simulations have made it clear that the effect of agitation of concentration boundary layer due to interfacial waves on the total mass transfer rate is small and a fluctuation of the Sherwood number is caused by a fluctuation of the bubble surface area. This result implies that interface tracking methods using boundary layer approximations can give accurate predictions for mass transfer from bubbles even when the flow field is not fully resolved when the wave effect on the net mass transfer is negligible. (C) 2013 Elsevier Ltd. All rights reserved.Lead, PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2014, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 58, 236 - 245, English[Refereed]Scientific journal
- To investigate the effects of hydrophilic particles on slurry bubble flows in a bubble column, distributions of the local gas holdup and the bubble frequency are measured using an electric conductivity probe. Particles are made of silica and their diameter is 100 mu m. The particle volumetric concentration C-S is varied from 0 to 0.40. The measured data imply that the presence of particles promotes bubble coalescence. The film drainage time for two coalescing bubbles in a quasi two-dimensional bubble flow in a small vessel is also measured to quantitatively evaluate the particle effect on coalescence. A particle-effect multiplier is introduced into a coalescence efficiency model by taking into account the data of film drainage time and is implemented into a multi-fluid model. The main conclusions obtained are as follows: (1) the local gas holdup and bubble frequency in slurry bubble flows decrease with increasing the particle concentration, (2) the hydrophilic particles enhance bubble coalescence and the enhancement saturates at C-S similar or equal to 0.45, (3) the particle effect on coalescence is well accounted for by introducing the particle-effect multiplier to the film drainage time, and (4) the multi-fluid model can give good predictions for the distribution of the local gas holdup in the slurry bubble column. (C) 2013 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2014, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 58, 154 - 167, English[Refereed]Scientific journal
- An interface-capturing method for simulating two-phase flows in complex geometries is proposed. A structured orthogonal grid is used, and the presence of stationary solid boundaries is taken into account by using the volume fraction of the solid phase in a computational cell. The transport equation of the fluid volume fraction in the presence of solid boundaries is derived. The fluid phases are transported by using the THAINC (tangent of hyperbola with adaptive slope for interface capturing) method. An immersed boundary method is implemented to accurately calculate the volume flux of each fluid phase through a computational cell face, a part of which is blocked by the solid phase. Transportation of a fluid square in the presence of solid boundaries is carried out, to con firm that the errors in shape and volume conservation are low. The applicability of the proposed method to two-phase flows in complex geometries is examined through simulations of a flow about cylindrical tubes in a staggered arrangement and a dam break problem with an obstacle. In the former the pressure drop in the single-phase condition agrees well with the available correlation and the gas-liquid behavior in the tube geometry is qualitatively well predicted. The predicted liquid flow in the dam break problem also agrees well with available experimental data.SOC CHEMICAL ENG JAPAN, 2014, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 47(3) (3), 230 - 240, English[Refereed]Scientific journal
- MASS TRANSFER FROM SINGLE CARBON DIOXIDE BUBBLES IN CONTAMINATED WATERMass transfer from single carbon dioxide bubbles rising through contaminated water in a vertical pipe of 12.5 mm diameter was measured to investigate effects of surfactant. The bubble diameter was widely varied to cover various bubble shapes such as spheroidal, wobbling, cap and Taylor bubbles. The gas and liquid phases were 99.9 % purity carbon dioxide and a surfactant solution made of purified water and Triton X-100. Comparison of mass transfer rates between contaminated and clean bubbles made clear that the surfactant decreases the mass transfer rates of small bubbles. The Sherwood number of small bubbles in the extreme cases, i.e. zero and the highest surfactant concentrations, is well correlated in terms of the bubble Reynolds number, Schmidt number and the ratio, lambda, of the bubble diameter to pipe diameter. The Sherwood numbers at intermediate surfactant concentration, however, are not well correlated using available correlations. The mass transfer rates of Taylor bubbles also decrease with increasing the surfactant concentration. They however increase with the diameter ratio and approaches that of clean Taylor bubbles as 2, increases. The main cause of this tendency was revealed by interface tracking simulations, i.e. the surfactant adsorbs only in the bubble tail region and the nose-to-side region is almost clean at high lambda.AMER SOC MECHANICAL ENGINEERS, 2014, ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING - 2014, VOL 1D: SYMPOSIA, FEDSM2014 - 21103, 8 pages, English[Refereed]International conference proceedings
- In this paper, we investigated the demulsification behavior of oil-in-water (O/W) emulsions during membrane permeation in the oil-water separation process using a numerical simulation approach. To accurately deal with the large deformation of the oil-water interface by coalescence and wetting, and to estimate the volume of the coalesced oil droplet, the coupled level set and volume-of-fluid method was used as the interface capturing method. We applied the simulation model to the permeation of O/W emulsions through a membrane pore, and then investigated the effects of the wettability of the membrane surface, filtration flux, and pore size on the demulsification efficiency. The results showed that oil droplets were likely to coalesce on the outlet membrane surface. High wettability on the membrane surface and low fluid velocity inside the pore increased the demulsification efficiency. This is the first work to numerically simulate the demulsification behavior of emulsions through membranes in the oil-water separation process.ROYAL SOC CHEMISTRY, 2014, SOFT MATTER, 10(40) (40), 7985 - 7992, English[Refereed]Scientific journal
- Experiments on bubbly flows in a rectangular column are carried out to investigate effects of inlet condition on How structure. An air diffuser having 35 nozzles is used. The inlet gas How rates from 34 nozzles are uniform and the lift coefficients of bubbles are small at this flow rate, whereas the gas inflow from the remaining one nozzle is varied to change the sign and magnitude of lift coefficients. The main conclusions obtained are as follows: (1) bubbly flow in a bubble column is apt to be heterogeneous even with small non-uniformity in the distribution of gas inflow; (2) when the nozzle causing non-uniform gas inflow is located in the center of the diffuser plate and the inflow distribution is symmetric, heterogeneous structure is formed mainly due to the lift-induced flow instability pointed out by Lucas et al. (2005); (3) when the nozzle causing non-uniform gas inflow is located near the side wall of the column and the inflow distribution is asymmetric, heterogeneous structure is induced by the Coanda effect; and (4) a multi-fluid model has a potential of predicting the effects of inlet condition on flow structure in a bubble column. (C) 2013 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2013, CHEMICAL ENGINEERING SCIENCE, 104, 166 - 176, English[Refereed]Scientific journal
- Immersed boundary-lattice Boltzmann methods (IB-LBM) with the single-relaxation time (SRT) cause non-physical distortion in fluid velocity when the Reynolds number is low, i.e. the relaxation time τ is high, and IB-LBM requires high spatial resolution to stably simulate high Reynolds number flows. An immersed boundary-finite difference lattice Boltzmann method (IB-FDLBM) using two-relaxation times (TRT) is therefore proposed in this study to simulate low and high Reynolds number flows stably and accurately. Benchmark problems such as circular Couette flows, flows past a circular cylinder and a sphere at various Reynolds numbers are carried out for validation. The main conclusions obtained are as follows: (1) TRT reduces numerical errors causing non-physical distortion in the fluid velocity at low Reynolds numbers, and accurate predictions are obtained when the parameter Λ, which is a function of the two relaxation times, is low, (2) for stable simulation the parameter Λ should be decreased as the Reynolds number increases, (3) implementation of TRT and the implicit direct forcing method into IB-FDLBM can solve two problems in simulation of low Reynolds number flows, i.e. non-physical velocity distortion and non-physical penetration of flow into the solid body, and (4) IB-FDLBM with TRT gives good predictions of the drag coefficients of a circular cylinder and a sphere in uniform flows for a wide range of the Reynolds number, Re, i.e., 0.1 ≤ Re ≤ 1x104.JSME, Sep. 2013, Journal of Fluid Science and Technology, 8(3) (3), 262 - 276, English[Refereed]Scientific journal
- Sep. 2013, 9th UK - Japan Seminar on Multi-Phase Flow, JapaneseGas-Liquid Two-Phase Flows Inside and Outside an Air Diffuser Pipe[Refereed]International conference proceedings
- Sep. 2013, 9th UK-Japan Seminar on Multi-Phase Flow, EnglishDistribution of Void Fraction and Liquid Velocity in Air-Water Bubble Column[Refereed]International conference proceedings
- In the present paper, a study of bubble dynamics in adiabatic conditions (i.e. with no heat and mass transfer) is carried out in order to understand the fundamental physics ruling the evolution of their interface, and open the way to the comprehension of more complex heat and mass transfer issues involving them. An external electric field is applied to the system to investigate the potentiality of this technique to enhance phase separation and heat transfer. A new numerical method for EHD action on a growing bubble has been developed combining VOF and level-set methods. To experimentally validate it, well-defined and simple boundary conditions have been selected: all the forms of heat and mass transfer have been excluded from the system, and an axisymmetric electric field configuration has been chosen in order to adopt a 2-D simulation. In the experimental apparatus a steady bubble stemming from an orifice in a still fluid (FC-72) has been produced, and a dc potential up to 20. kV was applied to a ring-shaped electrode coaxial with the orifice. In this way, in a first instance, all the dynamical effects have been eliminated, and a clear location of the three phase contact line, which is pinned to the orifice, has been defined. The bubble profile obtained from the experiment has been digitized and compared successfully with the outcomes of the numerical method. Furthermore, the study of the local curvature of the interface allowed the development of a new theory of the local electrical stress to be included in the capillary equation, which compares well with experimental data. Finally, the validated numerical method has been used to predict the bubble shape in the absence of gravity, in preparation of microgravity experiments. © 2013 Elsevier Inc.Sep. 2013, Experimental Thermal and Fluid Science, 49, 160 - 168, English[Refereed]Scientific journal
- Jun. 2013, 8th World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics (ExHFT8), USB memory, 8 pages, EnglishEffects of Inlet Condition on Flow Structure of Bubbly Flow in Rectangular Column[Refereed]International conference proceedings
- May 2013, 15th International Topical Meeting on Nuclear Reactor Thermal - Hydraulics, NURETH-15, NURETH15 - 244, USB memory, 12 pages, EnglishVoid Distribution and Bubble Motion in Bubbly Flows in a 4 X 4 Rod Bundle[Refereed]International conference proceedings
- May 2013, 15th International Topical Meeting on Nuclear Reactor Thermal - Hydraulics, NURETH-15, NURETH15 - 245, USB memory, 12 pages, EnglishNUMERICAL SIMULATION OF BUBBLY FLOWS IN A 4 X 4 ROD BUNDLE USING A MULTI-FLUID MODEL[Refereed]International conference proceedings
- May 2013, 8th International Conference on Multiphase Flow, ICMF2013, ICMF2013 - 229, USB memory, 9 pages, EnglishMass Transfer from Single Carbon Dioxide Bubbles in Glycerol-Water Solution[Refereed]International conference proceedings
- May 2013, 8th International Conference on Multiphase Flow, ICMF2013, ICMF2013 - 286, USB memory, 8 pages, EnglishEffects of Shape Oscillation on Mass Transfer from a Taylor Bubble[Refereed]International conference proceedings
- May 2013, 8th International Conference on Multiphase Flow, ICMF2013, ICMF2013 - 157, USB memory, 13 pages, EnglishEffects of Hydrophilic Particles on Bubble Coalescence in Slurry Bubble Column[Refereed]International conference proceedings
- Terminal velocities and shapes of drops rising through vertical pipes in clean and fully-contaminated systems are measured by using a high-speed video camera and an image processing method. Silicon oils and glycerol water solutions are used for the dispersed and continuous phases, respectively. Triton X-100 is used for surfactant. Clean and contaminated drops take either spherical, spheroidal or deformed spheroidal shapes when the diameter ratio λ is less than a critical value, λC, whereas they take bullet shapes for λ> λC (Taylor drops). The applicability of available drag and Froude number correlations is examined through comparisons with the measured data. Effects of surfactant on the shape and terminal velocity of a Taylor drop are also discussed based on the experimental data and interface tracking simulations. The conclusions obtained are as follows: (1) drag and Froude number correlations proposed so far give reasonable estimations of the terminal velocities of clean drops at any λ, (2) the terminal velocities of contaminated drops are well evaluated by making the viscosity ratio μ* infinity in the drag correlation for clean drops in the viscous force dominant regime, (3) the effects of surfactant on the shape and terminal velocity of a Taylor drop become significant as the Eötvös number, EoD, decreases and μ* increases, and (4) the reduction in surface tension due to the addition of surfactant would be the cause of the increase in the terminal velocity and elongation of a contaminated Taylor drop. © 2012 Elsevier Ltd.Mar. 2013, International Journal of Multiphase Flow, 49, 8 - 23, English[Refereed]Scientific journal
- The applicability of the immersed boundary-finite difference lattice Boltzmann method (IB-FDLBM) to high Reynolds number flows about a circular cylinder is examined. Two-dimensional simulations of flows past a stationary circular cylinder are carried out for a wide range of the Reynolds number, Re, i.e., 1 Re 1 105. An immersed boundary-lattice Boltzmann method (IB-LBM) is also used for comparison. Then free-falling circular cylinders are simulated to demonstrate the feasibility of predicting moving particles at high Reynolds numbers. The main conclusions obtained are as follows: (1) steady and unsteady flows about a stationary cylinder are well predicted with IB-LBM and IB-FDLBM, provided that the spatial resolution is high enough to satisfy the conditions of numerical stability, (2) high spatial resolution is required for stable IB-LBM simulation of high Reynolds number flows, (3) IB-FDLBM can stably simulate flows at very high Reynolds numbers without increasing the spatial resolution, (4) IB-FDLBM gives reasonable predictions of the drag coefficient for 1 Re1105, and (5) IB-FDLBM gives accurate predictions for the motion of free-falling cylinders at intermediate Reynolds numbers.Multi-Science Publishing, Mar. 2013, Journal of Computational Multiphase Flows, 5(1) (1), 27 - 41, English[Refereed]Scientific journal
- Dec. 2012, 計算数理工学論文集, Vol. 12, pp. 37-42, JapaneseNUMERICAL ANALYSIS OF THERMAL-HYDRAULICS BY IMMERSED BOUNDARY-LATTICE BOLTZMANN METHOD USING TWO-RELAXATION-TIME[Refereed]Scientific journal
- 日本計算数理工学会, Dec. 2012, ICOME2012/JASCOME2012, 12, 37 - 42, JapaneseNumerical analysis of thermal-hydraulics by immersed boundary-lattice Boltzmann method using two-relaxation-timeInternational conference proceedings
- Immersed boundary-lattice Boltzmann methods (IB-LBM) with the single-relaxation time (SRT) cause non-physical distortion in fluid velocity when the Reynolds number is low, i.e. the relaxation time τ is high, and IB-LBM requires high spatial resolution to stably simulate high Reynolds number flows. An immersed boundary-finite difference lattice Boltzmann method (IB-FDLBM) using two-relaxation times (TRT) is therefore proposed in this study to simulate low and high Reynolds number flows stably and accurately. Benchmark problems such as circular Couette flows, flows past a circular cylinder and a sphere at various Reynolds numbers are carried out for validation. The main conclusions obtained are as follows: (1) TRT reduces numerical errors causing non-physical distortion in the fluid velocity at low Reynolds numbers, and accurate predictions are obtained when the parameter Λ, which is a function of the two relaxation times, is low, (2) for stable simulation the parameter Λ should be decreased as the Reynolds number increases, (3) implementation of TRT and the implicit direct forcing method into IB-FDLBM can solve two problems in simulation of low Reynolds number flows, i.e. non-physical velocity distortion and non-physical penetration of flow into the solid body, and (4) IB-FDLBM with TRT gives good predictions of the drag coefficients of a circular cylinder and a sphere in uniform flows for a wide range of the Reynolds number, Re, i.e., 0.1 ≤ Re ≤ 1x104.The Japan Society of Mechanical Engineers, Dec. 2012, 9th International Conference on CFD in the Minerals and Process Industries,, CD-ROM, 6 pages(3) (3), 262 - 276, English[Refereed]International conference proceedings
- Dec. 2012, 9th International Conference on CFD in the Minerals and Process Industries,, CD-ROM, 6 pagesEFFECTS OF NUMERICAL TREATMENT OF VISCOUS AND SURFACE TENSION FORCES ON PREDICTED INTERFACE MOTION[Refereed]International conference proceedings
- Nov. 2012, Korea-Japan CFD Workshop 2012,, 8 pagesInterface Tracking Simulation of Bubbles in Clean and Contaminated SystemsInternational conference proceedings
- Sep. 2012, 6th Japanese-European Two-Phase Flow Group Meeting, USB memory, 10 pagesBUBBLE TRACKING SIMULATION OF BUBBLE-INDUCED PSEUDO TURBULENCE[Refereed]International conference proceedings
- A downscaled model of a steam separator is used to experimentally examine the effects of swirler shape on swirling annular flow. Several swirlers having different vane angles, different hub diameters, and different number of vanes are installed in the separator. Flow patterns, the ratio of the separated liquid flow rate to the total liquid flow rate, liquid film thickness, and pressure drop are measured. An improved swirler, which has a small hub diameter, the reduced number of vanes and modified vane shape, is also designed and its performance is examined. As a result, the following conclusions are obtained. (1)The reduction of the hub diameter and the number of vanes do not lower the separator performance. (2) The decrease in vane angle deteriorates the separation performance. This is due to the decrease in the centrifugal force, i.e., the decrease in the amount of droplet deposition. (3) The improved swirler effectively reduces the pressure drop while keeping high separator performance. (C) 2011 Elsevier B.V. All rights reserved.ELSEVIER SCIENCE SA, Aug. 2012, NUCLEAR ENGINEERING AND DESIGN, 249, 63 - 70, English[Refereed]Scientific journal
- Jun. 2012, International Conference on Numerical Methods in Multiphase Flows, No. 7-1Numerical Simulation of Mass Transfer From a Taylor Bubble with Shape OscillationInternational conference proceedings
- An immersed boundary-lattice Boltzmann method (IB-LBM) using a two-relaxation time model (TRT) is proposed. The collision operator in the lattice Boltzmann equation is modeled using two relaxation times. One of them is used to set the fluid viscosity and the other is for numerical stability and accuracy. Adirect-forcing method is utilized for treatment of immersed boundary. A multi-direct forcing method is also implemented to precisely satisfy the boundary conditions at the immersed boundary. Circular Couette flows between a stationary cylinder and a rotating cylinder are simulated for validation of the proposed method. The method is also validated through simulations of circular and spherical falling particles. Effects of the functional forms of the direct-forcing term and the smoothed-delta function, which interpolates the fluid velocity to the immersed boundary and distributes the forcing term to fixed Eulerian grid points, are also examined. As a result, the following conclusions are obtained: (1) the proposed method does not cause non-physical velocity distribution in circular Couette flows even at high relaxation times, whereas the single-relaxation time (SRT) model causes a large non-physical velocity distortion at a high relaxation time, (2) the multi-direct forcing reduces the errors in the velocity profile of a circular Couette flow at a high relaxation time, (3) the two-point delta function is better than the four-point delta function at low relaxation times, but worse at high relaxation times, (4) the functional form of the direct-forcing term does not affect predictions, and (5) circular and spherical particles falling in liquids are well predicted by using the proposed method both for two-dimensional and three-dimensional cases.Jun. 2012, Journal of Computational Multiphase Flows, 4(2) (2), 193 - 209, English[Refereed]Scientific journal
- Jun. 2012, 2012 Japan-U.S. seminar on Two-Phase flow Dynamics, USB memory, 10 pagesEFFECTS OF SURFACTANT ON THE MOTION OF BUBBLES IN LINEAR SHEAR FLOWSInternational conference proceedings
- Effects of the total gas flow rate on the water level in a diffuser pipe for a membrane bioreactor, the gas flow rate from each aeration hole and the bubble diameter are investigated. The diffuser has evenly positioned five aeration holes on the top and a larger hole on the bottom for introducing the liquid into the pipe. The gas flow rate from each aeration hole is measured by capturing generated bubbles. The water level and gas velocity inside the diffuser are computed by processing video images. The bubble diameter is calculated using the gas flow rate and the bubble generation frequency measured from the video images. The conclusions obtained are as follows: (1) the gas flow rate from the aeration hole depends on the water level inside the diffuser and becomes constant for all the holes as the total gas flow rate increases since the high total gas flow rate make the water level uniform, which results in a constant gas pressure in the diffuser, (2) the onset of slugging in the diffuser is well correlated in terms of the local gas velocity and the Mishima-Ishii's slugging model, (3) the increase in the total gas flow rate decreases the water level, causing suppression of the onset of slugging, (4) the diameter of aeration hole strongly affects the gas flow rate from each aeration hole and water level, and (5) the Davidson-Schuler correlation gives reasonable estimations of the bubble diameter, provided that the influence of slugging is not significant.The Japan Society of Mechanical Engineers, Apr. 2012, Journal of Fluid Science and Technology, Vol. 7, No. 1, pp. 78-88(1) (1), 78 - 88, English[Refereed]Scientific journal
- The purpose of this research was to provide further insights on bubble-induced agitation of heated bulk liquid. Fundamental studies on the bubble disturbance of a stratified thermal layer were carried out for a 6 mm sphere-volume equivalent diameter air bubble suspended in water (Eo=1.2). A video digital image system and thermochromic liquid crystals were used to reproduce the bubble movement as well as the wake drift of the liquid. A three-dimensional interface tracking simulation was used as a numerical tool. The results have revealed a long open wake region that is formed along the fluctuating bubble path. The amplitude of the bubble wake is much larger than that of the bubble path. In addition to longitudinal mixing, strong lateral mixing is also caused by the movement of vortices in the transverse direction. Details of numerical simulations have revealed a wake that tends to form a chain of Omega shaped vortex rings. These "rings" are connected to each other in the near wake region. The coherent effects further downstream lead to more complex vortex patterns in the far wake. The disintegration of the coherent chain of vortices due to bubble surface deformability is highly complex and not clear at this stage. A comparison with liquid crystal temperature response has revealed that the time scale of the mixing is much longer than the ascending bubble residence, approximately 8 s as obtained by several experimental runs. A transverse propagation of entrained cold water has given an estimate of the bubble-induced diffusion to be about 170 times larger than the diffusivity of momentum. The bulk liquid agitation cannot be correctly modeled without taking into account the bubble size dependent wake structure. (C) 2011 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2012, CHEMICAL ENGINEERING SCIENCE, 72, 155 - 171, English[Refereed]Scientific journal
- Mar. 2012, Journal of Computational Multiphase Flows, 3(4), 247-261Interface Tracking Simulation of Mass Transfer from a Dissolving Bubble[Refereed]Scientific journal
- Effects of soluble surfactant on the terminal velocity of a Taylor bubble rising through a vertical pipe are investigated using an interface tracking method. A level set method is utilized to track the interface. Transport of surfactant in the bulk liquid and at the interface is taken into account. The amount of adsorption and desorption is evaluated using the Frumkin and Levich model. The normal component of surface tension force is computed using a ghost fluid method, whereas the tangential component, i.e., the Marangoni force, is evaluated by making use of the continuum surface force model. Simulations of small air bubbles contaminated with soluble surfactant are carried out for validation. The Marangoni effects on the bubbles, i.e., the surface immobilization and the increase in drag coefficient, are well predicted. Then Taylor bubbles rising through vertical pipes filled with contaminated water at a low Morton number are simulated for various Eotvos numbers, various bulk surfactant concentrations and two different surfactants, i.e., 1-pentanol and Triton X-100. As a result, the following conclusions are obtained: (1) the reduction of surface tension near the bubble nose is the cause of the increase in terminal velocity, (2) the surfactant does not affect the terminal velocities of high Eotvos number bubbles since the bubbles at high Eotvos numbers are independent of surface tension, (3) the terminal velocity of a low Morton number Taylor bubble can be evaluated by making use of available correlations for clean Taylor bubbles, provided that the degree of contamination near the bubble nose is known and the Marangoni effect in the nose region is negligible, and (4) the Hatta number, which is the ratio of the adsorption velocity to the bubble velocity, is a primary factor governing the degree of contamination in the bubble nose region. (C) 2011 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Mar. 2012, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 39, 78 - 87, English[Refereed]Scientific journal
- An experimental study on countercurrent flow limitation (CCFL) in vertical pipes is carried out. Effects of upper tank geometry and water levels in the upper and lower tanks on CCFL characteristics are investigated for air-water two-phase flows at room temperature and atmospheric pressure. The following conclusions are obtained: (1) CCFL characteristics for different pipe diameters are well correlated using the Kutateladze number if the tank geometry and the water levels are the same; (2) CCFL occurs at the junction between the pipe and the upper tank both for the rectangular and cylindrical tanks, and CCFL with the cylindrical tank occurs not only at the junction but also inside the pipe at high gas flow rates and small pipe diameters; (3) the flow rate of water entering into the vertical pipe at the junction to the rectangular upper tank is lower than that to the cylindrical tank because of the presence of low frequency first-mode sloshing in the rectangular tank; (4) increases in the water level in the upper tank and in the air volume in the lower tank increase water penetration into the pipe, and therefore, they mitigate the flow limitation.HINDAWI PUBLISHING CORPORATION, 2012, SCIENCE AND TECHNOLOGY OF NUCLEAR INSTALLATIONS, No. NURETH14-057, CD-ROM (12 p, English[Refereed]Scientific journal
- An experimental study on countercurrent flow limitation (CCFL) in vertical pipes is carried out. Effects of upper tank geometry and water levels in the upper and lower tanks on CCFL characteristics are investigated for air-water two-phase flows at room temperature and atmospheric pressure. The following conclusions are obtained: (1) CCFL characteristics for different pipe diameters are well correlated using the Kutateladze number if the tank geometry and the water levels are the same; (2) CCFL occurs at the junction between the pipe and the upper tank both for the rectangular and cylindrical tanks, and CCFL with the cylindrical tank occurs not only at the junction but also inside the pipe at high gas flow rates and small pipe diameters; (3) the flow rate of water entering into the vertical pipe at the junction to the rectangular upper tank is lower than that to the cylindrical tank because of the presence of low frequency first-mode sloshing in the rectangular tank; (4) increases in the water level in the upper tank and in the air volume in the lower tank increase water penetration into the pipe, and therefore, they mitigate the flow limitation.HINDAWI PUBLISHING CORPORATION, 2012, SCIENCE AND TECHNOLOGY OF NUCLEAR INSTALLATIONS, Vol. 2012, 754724, 10 pages, English[Refereed]Scientific journal
- Bubble tracking simulations of bubbly flows in a rectangular column are carried out to examine the applicability of a bubble tracking method to flows involving the bubble-induced pseudoturbulence. Experimental data of void fraction, mean liquid and bubble velocities, and liquid fluctuation velocity are obtained for validation. As a result, the following conclusions are obtained: (1) The order of liquid fluctuation velocity is similar to that of the bubble relative velocity, and the fluctuation is well scaled in terms of the bubble terminal velocity and the void fraction, as Risso & Ellingsen suggested [J. Fluid Mech., vol. 440, pp. 235-268, 2001]. (2) The Reynolds shear stress is not produced by the bubble motion when both void fraction and liquid velocity are uniform. (3) The Reynolds stress model proposed by Lopez de Bertodano et al. [Int. J. Multiphase Flow, vol. 20, pp. 805-818, 1994] underestimates the normal stress, whereas the bubble tracking simulation with a spatial resolution comparable to the bubble size gives better predictions than the model. (4) The fluctuation in liquid velocity induced by bubbles is partly resolved with a spatial resolution comparable to the bubble size, and subgrid turbulence models do not have much influence on predictions. (5) Eddy viscosity models would be a reasonable choice to capture the shear-induced turbulence in the near-wall region in bubbletracking simulations with an inevitably insufficient spatial resolution for large eddy simulation. © 2012 by Begell House, Inc.Begell house, 2012, Multiphase Science and Technology, 24(3) (3), 197 - 222, English[Refereed]Scientific journal
- An immersed boundary method based on a finite difference lattice Boltzmann method (IB-FDLBM) is presented. The FDLBM solves the discrete Boltzmann equation including an additional collision term by using finite difference schemes. The additional term works as a negative viscosity in the macroscopic level and allows us to alter the fluid viscosity while keeping the other relevant parameters of the simulation fixed. The immersed boundary method employs a direct-forcing method, which utilizes external forces at Lagrangian points embedded on immersed boundaries to impose the no-slip boundary condition. Several benchmark simulations are carried out to validate the developed method, i.e., flows past a circular cylinder, a falling particle, and interaction between two falling particles. Couette flows between a stationary and a rotating cylinder are also simulated at various values of the relaxation time for collision. The main conclusions obtained are as follows: (1) steady flows past a stationary circular cylinder are well predicted, (2) the motions of particles falling through liquids predicted using IB-FDLBM quantitatively agree well with those obtained using immersed boundary methods based on the lattice Boltzmann equation (IB-LBM), (3) the developed method well predicts the interaction between two particles falling through a liquid, e.g., the drafting-kissing-tumbling motion, and (4) distortion of velocity fields in circular Couette flows at high relaxation times is removed by the additional collision term.The Japan Society of Mechanical Engineers, Dec. 2011, Journal of Fluid Science and Technology, 6(6), 1051-1064(6) (6), 1051 - 1064, English[Refereed]Scientific journal
- Oct. 2011, Proc. of 1st International Symposium on Multiscale Multiphase Process Engineering (MMPE), CD-ROM (6 pages)Multiscale Simulation of Dispersed Flow in Bubble ColumnsInternational conference proceedings
- Sep. 2011, International Conference on Advanced Technology in Experimental Mechanics 2011Mass transfer from a dissolving carbon dioxide bubble in glycerol-water solutionInternational conference proceedings
- Sep. 2011, International Conference on Advanced Technology in Experimental Mechanics 2011Assessment of turbulence models for bubbly flow in a bubble columnInternational conference proceedings
- Jun. 2011, 8th International Conference on COMPUTATIONAL FLUID DYNAMICS in the Oil & Gas, Metallurgical and Process IndustriesInterface tracking and multi-fluid simulation of bubbly flows in bubble columnsInternational conference proceedings
- May 2011, 49th European Two-Phase Flow Group MeetingInterface tracking simulation of dissolving bubbles and of contaminated bubbles and dropsInternational conference proceedings
- A scaling analysis based on the field equations for two phases and the jump conditions at the interface is carried out to deduce a balance of forces acting on a Taylor drop rising through stagnant liquid in a vertical pipe. The force balance is utilized to deduce a functional form of an empirical correlation of terminal velocity of the Taylor drop. Undetermined coefficients in the correlation are evaluated by making use of available correlations for two limiting cases, i.e. extremely high and low Reynolds number Taylor bubbles in large pipes. Terminal velocity data obtained by interface tracking simulations are also used to determine the coefficients. The proposed correlation expresses the Froude number Fr as a function of the drop Reynolds number Re-D, the Eotvos number Eo(D) and the viscosity ratio mu*. Comparisons between the correlation, simulations and experimental data confirm that the proposed correlation is applicable to Taylor drops under various conditions, i.e., 0.002 < Re-D < 4960, 4.8 < Eo(D) < 228, 0 <= mu* <= 70, 1 < N < 14700, -12 < log M < 4, and d/D < 1.6, where N is the inverse viscosity number, M the Morton number, d the sphere-volume equivalent drop diameter and D the pipe diameter. (C) 2010 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Apr. 2011, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 37(3) (3), 241 - 251, English[Refereed]Scientific journal
- MASS TRANSFER FROM A BUBBLE IN A VERTICAL PIPEMass transfer from single carbon dioxide bubbles in a vertical pipe is measured using a stereoscopic image processing method to develop a mass transfer correlation applicable to a wide range of bubble and pipe diameters. The pipe diameters are 12.5, 18.2 and 25 0 mm and the bubble diameter ranges from 5 to 26 mm The ratio, lambda, of bubble diameter to pipe diameter is therefore varied from 0.2 to 1.8, which covers various bubble shapes such as spherical, oblate spheroidal, wobbling, cap, and Taylor bubbles. Measured Sherwood numbers, Sh, strongly depend on bubble shape, i.e., Sh of Taylor bubbles clearly differs from those of spheroidal and wobbling bubbles. Hence two Sherwood number correlations, which are functions of the Peclet number and the diameter ratio lambda, are deduced from the experimental data: one is for small bubbles (lambda < 0.6) and the other for Taylor bubbles (lambda > 0.6). The applicability of the proposed correlations for the prediction of bubble dissolution process is examined through comparisons between measured and predicted long-term bubble dissolution processes. The predictions are carried out by taking into account the presence of all the gas components in the system of concern, i.e. nitrogen, oxygen and carbon dioxide. As a result, good agreements for the dissolution processes for various bubble sizes and pipe diameters are obtained. It is also demonstrated that it is possible to evaluate an equilibrium bubble diameter and instantaneous volume concentration of carbon dioxide in a bubble using a simple model based on a conservation of gas components.AMER SOC MECHANICAL ENGINEERS, 2011, PROCEEDINGS OF THE ASME/JSME 8TH THERMAL ENGINEERING JOINT CONFERENCE 2011, VOL 1 PTS A AND B, AJTEC2011-44089, 9 pages, 1363 - +, English[Refereed]International conference proceedings
- An interface tracking method for predicting motions of bubbles contaminated with soluble surfactants is presented. A level set method is utilized to track the interface. Transportations of surfactants in the bulk liquid and those at the interface are taken into account. The amount of adsorption and desorption is evaluated by using the Frumkin & Levich model. Simulations of bubbles contaminated with soluble surfactants are carried out, i.e., single air bubbles rising through stagnant water, Taylor bubbles in a vertical pipe filled with water, and a wobbling bubble in a vertical duct. As a result, the following conclusions are obtained: (1) the increase in drag coefficients of spherical bubbles due to the presence of surfactant, i.e. Marangoni effect, is well predicted, (2) surfactants mainly accumulate at the rear edge of a Taylor bubble and the Marangoni effect is very small in the nose region at high Eötvös and low Morton numbers, and therefore, the effects of surfactant on the bubble rising velocity are small in low viscosity systems, and (3) the surfactant concentration is low in the top region of a wobbling bubble, whereas it is high in the bottom region. The peak concentration appears at the side edge of the bubble and the location of the peak concentration moves with the bubble and wake movements. Copyright © 2011 by ASME.2011, ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011, 1(D) (D), 1641 - 1650, English[Refereed]International conference proceedings
- An interface tracking method for predicting bubble dissolution process is proposed. A non-diffusive scheme for advecting species concentrations is adopted to accurately compute the volume change due to mass transfer. The applicability of the proposed method is examined through several benchmark tests, i.e. mass transfer from a static bubble and that from free rising bubbles. Predicted species concentration distributions and mass transfer coefficients agree well with theoretical and empirical models. Dissolution of single carbon dioxide bubbles in a vertical pipe filled with water is also simulated. The bubbles consist only of carbon dioxide, and nitrogen and oxygen are initially dissolved in water. The volume change due to dissolution of carbon dioxide from the bubbles and evaporation of nitrogen and oxygen from water are well predicted. such as mass transfer from a stationary bubble, that from free rising bubbles, and single dissolving carbon dioxide bubbles in a vertical pipe filled with water. Copyright © 2011 by ASME.2011, ASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011, 1(D) (D), 1593 - 1601, English[Refereed]International conference proceedings
- Three-dimensional interface tracking simulations were carried out to investigate the role of surface tension force in the process of vapor bubble lift-off from a hydrophilic heated surface in nucleate boiling. Since bubbles are frequently flattened along the heated surface in photographic experiments reported in literature, a bubble was assumed to be spheroidal in shape in the initial condition. The effect of phase change at the bubble interface was not taken into consideration for the sake of simplicity. In the present numerical simulations, the initially spheroidal bubble approached the spherical shape due to the surface tension force and was eventually lifted off the surface. The change in bubble shape induced local liquid flow directing toward the bubble base, that was the direct cause of the occurrence of the bubble lift-off. The dependence of the bubble migration velocity on several important parameters including the bubble size, surface tension coefficient and the density of surrounding liquid was also investigated. The change in bubble shape from flattened to more rounded causes the reduction of the surface energy, while the formation of local liquid flow leads to an increase in the kinetic energy. It was demonstrated that the bubble migration velocity after the lift-off can successfully be interpreted from the standpoint of energy conservation during the lift-off process. (c) 2010 Elsevier B.V. All rights reserved.ELSEVIER SCIENCE SA, Dec. 2010, NUCLEAR ENGINEERING AND DESIGN, 240(12) (12), 3942 - 3948, English[Refereed]Scientific journal
- This paper investigates flow patterns encountered in two-phase swirling flow in a vertical pipe. Flows in the pipe are observed by using a high-speed video camera and the void fractions are calculated from the video images. Flows at various gas and liquid volumetric fluxes, JG and JL, are tested, i.e., 0.01 ≤ JG ≤ 8 m/s and 0.10 ≤ JL ≤ 0.80 m/s. When JL is higher than a certain value, no bubbles exist in a swirling flow but a gas column forms due to the centrifugal force even at low JG. The diameter of a gas column increases with JG at a constant JL. A tornado-shaped gas column forms at intermediate JG. At high JG, a liquid film including small bubbles and intermittent liquid slugs with many bubbles are observed. These flows are classified into four flow patterns based on the observations and the characteristics of void fraction. The statistical quantities of void fraction, i.e., the mean, standard deviation, skewness and kurtosis, are also computed. The validity of the flow pattern classification based on the statistical quantities has been confirmed.THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Sep. 2010, Japanese Journal of Multiphase Flow, Vol. 24, No. 3, pp. 305-312(3) (3), 305 - 312, Japanese[Refereed]Scientific journal
- Sep. 2010, 8th Japan-UK Seminar on Multiphase FlowsInterface Tracking simulation of mass transfer from a dissolving bubble in a vertical pipeInternational conference proceedings
- Jun. 2010, 48th European Two-Phase Flow Group Meeting 2010, ETPFGM'10Agitation of thermally stratified water layer by free rising wobbling air bubbleInternational conference proceedings
- May 2010, Proc. of 7th International Conference on Multiphase Flow, ICMF2010, 13 pagesTerminal velocity of a Taylor drop in a vertical pipe[Refereed]International conference proceedings
- May 2010, Proc. of International Conference on Multiphase Flow, ICMF2010, 11 pagesTerminal velocity of a single drop in a vertical pipe in clean and fully-contaminated systems[Refereed]International conference proceedings
- May 2010, Proceedings of 7th International Conference on Multiphase Flow, No. 2-1-2, EnglishLES-Based Bubble Tracking Simulation of Turbulent Cavitation Flow in Injector Nozzle[Refereed]International conference proceedings
- Mar. 2010, Japanese Journal of Multiphase Flow, Vol. 23, No. 5, pp. 547-554, Japanese[Refereed]Scientific journal
- 神戸市立工業高等専門学校, Mar. 2010, Research reports of Kobe city college of technology, No. 48, pp. 45-50(48) (48), 45 - 50, JapaneseStudy on interface tracking method based on unstructured grid[Refereed]Scientific journal
- Mar. 2010, 神戸高専研究紀要, 49, JapaneseStudy on decompression of floatation thickening of activated sludge[Refereed]Scientific journal
- 神戸市立工業高等専門学校, Mar. 2010, Research reports of Kobe city college of technology, No. 48, pp. 39-44(48) (48), 39 - 44, JapaneseT字形エルボによるキャビテーション壊食対策に関する研究[Refereed]Scientific journal
- Interface tracking simulations of single drops rising through a vertical pipe are carried out using three coordinate systems, i.e. cylindrical, general curvilinear and Cartesian coordinates, to investigate the effects of coordinate system and spatial resolution on the accuracy of predictions. Experiments of single drops in a vertical pipe are also conducted to obtain experimental data for comparisons with simulations. The drop shape observed are spheroidal and deformed spheroidal at low values of the diameter ratio, λ, of the sphere-volume equivalent diameter of a drop to the pipe diameter, whereas they take bullet-shapes at large λ. The conclusions obtained are as follows: (1) the effects of coordinate system on drop shape are small at low λ. At large λ, the effects are also small for drops in a low viscosity system, whereas non-physical shape distortion takes place when the Cartesian coordinates are used with low spatial resolution for drops in a high viscosity system, and (2) the drop terminal velocity and the velocity profile in the liquid film between a bullet-shaped drop and a pipe wall are well predicted using all the coordinate systems tested even at low spatial resolution.Mar. 2010, Journal of Computational Multiphase Flows, 2(1) (1), 47 - 57, English[Refereed]Scientific journal
- 2010, The 8th Japan-UK Seminar on Multiphase FlowBubble Coalescence in a Slurry Bubble ColumnInternational conference proceedings
- An Evolving Numerical Method for Designing Slurry Bubble Column ReactorsA numerical method for simulating gas-liquid-solid three-phase flows in a slurry bubble column reactor was developed based on a mixing model and an artificial neural network (ANN). Macroscopic variables required for the mathematical closure of the mixing model, such as the gas holdup, dispersion coefficient, and reaction rate, were evaluated by use of ANN, rather than empirical correlations. In contrast to the empirical correlations, ANN possesses the following advantages: (1) it is applicable to a wide range of flow conditions owing to its generalization ability, and (2) the accuracy is easily improved through a learning process using an up-to-date database. For the validation of ANN, gas holdups in an air-water bubble column were measured. Then simulations of gas-liquid-solid three-phase flows in a Fischer-Tropsch (FT) reactor were carried out using the combination of the mixing model and ANN to demonstrate its potential. The results obtained are as follows: (1) ANN accurately evaluates the gas holdups in the air-water bubble column, (2) the combination of the mixing model and ANN gives good predictions for CO conversions in FT synthesis, and (3) the accuracy of ANN is easily improved through the re-learning process. These results imply that the proposed method can be a framework for simulating multiphase flows in large industrial systems.SOC CHEMICAL ENG JAPAN, 2010, KAGAKU KOGAKU RONBUNSHU, 36(1) (1), 17 - 24, Japanese[Refereed]Scientific journal
- An empirical correlation of the terminal velocity of a Taylor bubble in a vertical pipe is proposed. A fundamental functional form, Fr = f (Re D, EoD), of the correlation is deduced by carrying out a dimensional analysis based on the local instantaneous field equations and the jump conditions. Here Fr is the Froude number, ReD the bubble Reynolds number, and EoD the Eötvös number. In the two limiting cases, (EoD →∞ and ReD →∞) and (EoD →∞ and ReD → 0), the deduced functional form approaches those of the well-known Fr models. Coefficients appearing in the correlation are determined by making use of the limiting cases and available experimental data. Comparisons between the proposed Fr correlation and the experimental data show that the correlation gives a good estimation of terminal velocities of Taylor bubbles for a wide range of fluid properties and pipe diameters, i.e., 10-7 < ReD < 104, 4 < EoD < 3 × 103, 10-2 < N < 105, and -11 < log M < 10, where N is the inverse viscosity number and M the Morton number. © 2010 by Begell House, Inc.2010, Multiphase Science and Technology, 22(3) (3), 197 - 210, English[Refereed]International conference proceedings
- Bubble coalescence and breakup models are implemented into the (N+2)-field model, which is a hybrid combination of a multi-fluid model and an interface tracking method to examine the applicability of available bubble coalescence and breakup models to poly-dispersed bubbly flows in bubble columns. The implemented models are a breakup model proposed by Luo & Svendsen and coalescence models proposed by Prince & Blanch and Wang et al. The validation of these models is carried out using experimental data for a coalescence-dominating flow, a breakup-dominating flow, a flow in-between, and a flow with low coalescence-breakup frequencies. Good predictions of void and bubble size distributions for the four kinds of poly-dispersed bubbly flows in bubble columns are obtained. It is also demonstrated that all the possible bubble coalescence mechanisms, i.e. bubble coalescence caused by bubble collisions due to turbulent eddies, the difference in bubble velocities and shear slip, and bubble coalescence due to wake entrainment, should be taken into account for obtaining good predictions.The Japan Society of Mechanical Engineers, Nov. 2009, Transaction of the Japanese Society of Mechanical Engineers, 75-759, pp.2182-2189(759) (759), 2182 - 2189, Japanese[Refereed]Scientific journal
- Numerical simulations based on a three-dimensional two-way bubble tracking method are carried out to predict bubble motions in a square duct with an obstacle and in a two-by-three rod bundle with a grid spacer. Comparisons between measured and predicted bubble motions demonstrate that the two-way bubble tracking method gives good predictions for trajectories of small bubbles in the upstream side of the grid spacer in the rod bundle geometry. The predicted bubble trajectories clearly show that bubbles are apt to migrate toward the rod surface in the vicinity of the bottom of the grid spacer. Analysis of forces acting on the bubbles confirms that pressure gradient force induced by the presence of the spacer is the main cause of the bubble lateral migration toward the rod surface. Motions of steam bubbles at a nominal operating condition of a pressurized water reactor (PWR) are also predicted by using the bubble tracking method, which indicates that steam bubbles also migrate toward the rod surface at the upstream side of the spacer due to the spacer-induced pressure gradient force.The Japan Society of Mechanical Engineers, Sep. 2009, Journal of Power and Energy Systems, Vol. 3, No. 2, pp. 393 - 404(2) (2), 393 - 404, English[Refereed]Scientific journal
- Sep. 2009, 5th EuropeanTwo-Phase Flow Group Meeting, CD-ROM, 9 pages, EnglishDissolution of Carbon Dioxide Bubbles in Clean and Contaminated Systems[Refereed]International conference proceedings
- Sep. 2009, 5th EuropeanTwo-Phase Flow Group Meeting, CD-ROM, 6 pages, EnglishDimensional Analysis of Terminal Velocityof a Taylor Bubble in a Vertical Pipe[Refereed]International conference proceedings
- A drag correlation for a fluid particle rising along the axis of a vertical pipe at low and intermediate Reynolds numbers, Re, is proposed by making use of available correlations and a numerical database accumulated by interface tracking simulations. The accuracy of the interface tracking method has been verified through comparisons between measured and predicted velocities of single drops in vertical pipes. Being similar to drag model for solid spheres proposed by Michaelicles, the developed drag correlation takes into account inertial and wall effects as their linear combination. The correlation gives good estimation of the drag coefficient for fluid particles rising through stagnant liquids in vertical pipes under the conditions of 0.13 <= Eo <= 30, -10.0 <= logM <= 2.0, 0.083 <= Re < 200, 0 <= kappa <= 10.0 and lambda <= 0.6, where Eo is the Eotvos number, M the Morton number, K the viscosity ratio and A the ratio of particle diameter to pipe diameter. (C) 2009 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, Jun. 2009, CHEMICAL ENGINEERING SCIENCE, 64(12) (12), 3019 - 3028, English[Refereed]Scientific journal
- 神戸市立工業高等専門学校, Mar. 2009, Research reports of Kobe city college of technology, No. 47, pp. 13-18(47) (47), 13 - 18, JapaneseReduction of frictional pressure drop in micro bubble flow in a horizontal pipe[Refereed]Scientific journal
- 神戸市立工業高等専門学校, Mar. 2009, Research reports of Kobe city college of technology, No. 47, pp. 19-24(47) (47), 19 - 24, JapaneseFlow pattern of swirling gas-liquid two-phase flow in a vertical pipe and a flow-pattern identification method[Refereed]Scientific journal
- The purpose of this study is to develop a practical numerical method for predicting multiphase flows in industrial systems of large scale. The practical method should be equipped with two functions. One is the ability of dealing with complex geometry of a given practical system without time-consuming grid generation procedures. The other is to simulate flows in large complex systems without using a high number of computational cells. Therefore, a numerical method based on the combination of a multifluid and interface tracking method and an immersed boundary method is proposed in this study. The hybrid combination of the multifluid and interface tracking methods enables us to simulate multiphase flows with various scales and various phases, and the immersed boundary method makes it possible to satisfy the two requirements. Several numerical simulations are carried out to demonstrate the potential of the proposed method. Comparisons between measured and predicted bubbly flows around single obstacles prove that the proposed method gives reasonable predictions for the interaction between bubbly flow and structures. Simulation of a bubble column with complex structure demonstrates its applicability to large industrial systems.Begell House Inc., 2009, Multiphase Science and Technology, 21(1-2) (1-2), 141 - 155, English[Refereed]Scientific journal
- Jul. 2008, Proc. 5th International Conference on Transport Phenomena in Multiphase Systems, CD-ROM, EnglishSingle Drops Rising Through Stagnant Liquids in a Vertical Pipe[Refereed]International conference proceedings
- Flow characteristics of cavitating flow in a T-shape elbowWater is more liable to evaporate than oils since its saturated vapor pressure is higher than the ones of oils. Therefore it is important to prevent erosion due to cavity in hydraulic devices using water. In our previous study, we reported that erosion at elbow of pipeline can be reduced by using T-shape elbow. However its mechanism has not been clarified yet. In the present study, we observed cavitating flows in T-shape elbows with different shapes using a digital and high-speed video cameras. The amount of cavity was evaluated from taking images. As a result we confirmed that (1) circulating flow is steadily formed when the length of cavity-trapping region L ≥ 22.5 mm. If L ≤ 15 mm, circulating flow is formed intermittently, or it is not formed, (2) The amount of cavity in cavity-trapping region increases with L, and (3)there are two uses (a) T-shape elbows can be used to guide cavity into the region, in which circulating flow is formed, for defending the downstream of pipeline, and (b) Then the elbows can also be used to guide bubbles to the downstream so as to prevent erosion at the elbows.Kobe City College of Technology, Mar. 2008, Research reports of Kobe city college of technology, No. 46, pp. 13-18, 13 - 18, Japanese[Refereed]Scientific journal
- 2008, Proc. 6th Japan-Korea Symp. Nuclear Thermal Hydraulics and Safety, CD-ROM, pp.1-8, EnglishA Numericsl Study on the Mechanism of Vapor Bubble Lift-off from a Flat Plate[Refereed]International conference proceedings
- The number of computational cells assigned to a small bubble is liable to be small in a volume tracking simulation of a poly-dispersed bubbly flow. The volume tracking method is, therefore, expected to at least give qualitatively reasonable predictions of bubble motion without assigning many cells. In this study, bubble motions in stagnant water and shear flows are simulated with low spatial resolutions using a volume tracking method proposed in our previous study. As a result, we confirm that (1) the method can yield correct characteristics of rising velocity and lateral motion of bubbles, and (2) the bubble volume and interface sharpness are kept well even after a bubble had experienced a large deformation in a strong shear flow.The Japan Society of Mechanical Engineers, Dec. 2007, Journal of Fluid Science and Technology, Vol. 2, No. 2, pp. 490-501(2) (2), 490 - 501, English[Refereed]Scientific journal
- The interface tracking method based on a nonuniform subcell scheme (NSS) and a level set function (LS) is applied to three-dimensional (3-D) general curvilinear and cylindrical coordinate systems. The method for 3-D general curvilinear coordinates is based on the combination of NSS, LS, a finite volume method, and a multiblock method. The method for cylindrical coordinates is based on the combination of NSS, LS, the variable transformation proposed by Verzicco and Orlandi (1996), and a simple method for evaluating surface tension force at the singular point r 0. Simulations of single air and vapor bubbles in rod bundle geometry are carried out using the former method. Predicted bubble shapes and terminal velocities agree well with measured data and an available terminal velocity model. Bubbles and drops in pipes are simulated using the latter method. Terminal velocities of single drops confined in a pipe are well predicted. The bouncing motion of an air bubble in a laminar water flow in a vertical pipe is successfully simulated. Volumes of bubbles and drops are well conserved in all simulations.2007, Multiphase Science and Technology, 19(2) (2), 121 - 140, English[Refereed]Scientific journal
- Numerical simulation of single drops in a vertical pipe using various coordinate systemsThe effects of the diameter ratio lambda (=d/D, where d and D are the diameters of a drop and a pipe, respectively), the Morton number M and the viscosity ratio kappa (= mu(d)/mu(c), where mu is the viscosity and the Subscripts d and c are the dispersed fluid particle and the continuous phase, respectively) on terminal velocities and shapes of single drops rising through stagnant liquids in a vertical pipe are investigated experimentally. Then, the drops in the pipe are simulated using a volume tracking method with various coordinate systems, i.e., three-dimensional (3D) cylindrical coordinates, 3D general curvilinear coordinates and 3D Cartesian coordinates. Predicted velocities and shapes of the drops using three coordinate systems are compared with the measured data to examine the effects of coordinate systems on the accuracy of prediction. As a result. (1) The velocity ratio V-T/V-T0 (V-T and V-T0 are the terminal velocity in a pipe and infinite liquid, respectively) decreases as lambda increases, and it depends not only on lambda but also on M and kappa, (2) Good predictions for the terminal velocities and shapes of drops Lire obtained not only with cylindrical coordinates and Curvilinear coordinates but also with Cartesian coordinates, provided that the spatial resolution is high, (3) When the spatial resolution is low, effects of coordinate systems on a drop shape are larger for Cartesian coordinate systems than for cylindrical coordinate and general Curvilinear coordinate systems, and (4) Errors in predicted drop velocities are not so large even with very low spatial resolution.AMER SOC MECHANICAL ENGINEERS, 2007, FEDSM 2007: PROCEEDINGS OF THE 5TH JOINT ASME/JSME FLUIDS ENGINEERING SUMMER CONFERENCE, VOL 2, PTS A AND B, CD-ROM, FEDSM2007-37491, 291 - 296, English[Refereed]International conference proceedings
- Qualitative Validity of Volume Tracking Simulation of Bubble Motion with Low Spatial ResolutionThe number of computational cells assigned to a small bubble is liable to be small in a volume tracking simulation of a poly-dispersed bubbly flow. The volume tracking method is, therefore, expected to at least give qualitatively reasonable predictions of bubble motion without assigning many cells. In this study, bubble motions in stagnant water and shear flows were simulated with low spatial resolutions using a volume tracking method proposed in our previous study. As a result, we confirmed that (1) the method could yield correct characteristics of rising velocity and lateral motion of bubbles, and (2) the bubble volume and interface sharpness were kept well even after a bubble had experienced a large deformation in a strong shear flow.The Japan Society of Mechanical Engineers, Oct. 2006, 日本機械学会論文集, Vol. 72, No. 722, (B), pp. 241(722) (722), 2410 - 2417, Japanese[Refereed]Scientific journal
- Sep. 2006, Japanese Journal of Multiphase Flow, 20巻3号, pp.244-251, Japanese[Refereed]Scientific journal
- Sep. 2006, 4th Japanese-European Two-Phase Flow Group Meeting, CD-ROM (8 pages)Interface Tracking Simulation of Bubbles and Drops in Complex Geometries[Refereed]International conference proceedings
- Jul. 2006, Computational Fluid Dynamics Journal, Vol. 15, Iss. 2, pp. 225-232, EnglishA Volume Tracking Method Based on Non-Uniform Subcells and Continuum Surface Force Model Using a Local Level Set Function[Refereed]Scientific journal
- Computational Multi-Fluid Dynamics, CMFD, has come to play an important role in practical engineering and fundamental researches on multiphase flows. Since a multiphase flow is often comprised of interdependent elementary phenomena with length scales ranging from mesoscale to macroscale, a multipurpose CMFD should cover a wide range of scales by the combination of different numerical methods such as interface tracking, bubble tracking and averaging methods. This report reviews recent activities on CMFD for bubbly flows, in particular, an improvement of an interface tracking method based on volume tracking, two types of hybrid CMFD methods based on a combination of interface tracking and bubble tracking methods and that of interface tracking and averaging methods, and work in progress heading toward the hybrid combination of the three methods.2006, Multiphase Science and Technology, 18(1) (1), 73 - 110, English[Refereed]Scientific journal
- Sep. 2005, Proc. Int. Minisymposium on Challenger and Adavances in Flow SImulation and Modeling, p.276, EnglishToward Hybrid Simulation of Bubbly Flow (Invited Lecture)International conference proceedings
- A volume tracking method based on Advanced Subgrid Counting AlgorithmA volume tracking scheme, ASCA (Advanced Subgrid Counting Algorithm), which is easily extendable to three-dimensions and possesses a good volume conservation property, is proposed. To examine the potential of ASCA, several two-phase flow simulations are carried out. As a result, the following conclusions are obtained: (1) Predicted shapes and breakup characteristics of single fluid particles in simple shear flows agree well with available data even with a low spatial resolution, (2) A water drop impinging on water surface and an air bubble rising through a stagnant water are successfully simulated with little errors in volume conservation, (3) Predicted shapes and terminal velocities of single drops in stagnant liquids under wide ranges of the viscosity ratio and Morton number agree well with measured one, and (4) In spite of a low spatial resolution, vapor bubbles flowing in a strong shear flow are simulated with good volume conservation. The interface sharpness is well preserved even after a large deformation of bubbles.AMER SOC MECHANICAL ENGINEERS, 2005, Proceedings of the ASME Fluids Engineering Division Summer Conference, Vol 2, CD-ROM, FEDSM2005-77396, 265 - 270, English[Refereed]International conference proceedings
- 2004, Proc.6th US-Japan Seminar on Two-Phase Flow Dynamics, 1,1-16, EnglishModelong and Hybrid Simulation of Bubbly Flow(Keynote Lecture)[Refereed]International conference proceedings
- The validity of the Simple Counting Algorithm (SCA) for the volume tracking simulations of a single bubble in stagnant liquid is examined. As a result, it is confirmed that (i) the SCA can keep sharp interface, but (ii) the volume of bubble is increased. An improved SCA is proposed in order to reduce the volume error. Numerical simulations of a single air bubble rising in stagnant water are carried out using a course grid. i.e. only 6 cells to the bubble equivalent diameter. The volume of bubble is conserved well and a sharp interface is kept for as long as 12 seconds.Japan Society of Mechanical Engineers, 2004, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70(698) (698), 2538 - 2544, English[Refereed]Scientific journal
- Jul. 2003, Proc. 4th ASMER-JSME Joint Fluids Engineering Conf., CD-ROM, EnglishEvaluation of Volume Tracking Algorithms for Gas-Liquid Two-Phase Flows.[Refereed]International conference proceedings
- Numerical analysis of methanol droplet combustion in hot air flowNumerical analysis on evaporation and combustion phenomena of a deforming methanol droplet in a hot air flow was carried out in the present study. An interface tracking method, the Volume of Fluid (VOF) method, was employed to predict the droplet deformation. This approach holds a high potential to simulate the spray combustion including many deforming droplets moving freely in a gas flow using a Eulerian mesh. The advance of the gas-liquid interface in time was predicted by the CIP scheme to avoid numerical diffusion of gas-liquid interface. The numerical calculation of the evaporation and ignition of a single methanol droplet in a hot stagnant air was conducted to clarify the validity of the numerical method. Then the numerical simulation of the ignition and transient flame behavior of a deforming droplet in convective hot air flow was carried out, and the envelope flame developed around a fuel droplet was reasonably predicted. The effects of numerical scheme on calculated results were also examined.SOUTHEAST UNIV PRESS, 2003, COMBUSTION SCIENCE AND TECHNOLOGY IN ASIA-PACIFIC AREA: TODAY AND TOMORROW, Paper No.071, 509 - 512, English[Refereed]International conference proceedings
- Numerical analysis of ignition and combustion of a deformable dropletA numerical analysis was conducted to predict the evaporation and combustion phenomenon of droplets with free moving interface. An interface tracking method, the Volume of Fluid (VOF) method, was assigned to predict the droplet motion, which has a high potential to simulate the spray phenomena including many deforming droplets moving freely with each velocity in the surrounding gases. A one-step global reaction of methanol vapor in air was assigned to predict chemical reaction, and the reaction rate was given by the Arrhenius law at the first step. The numerical simulation of the evaporation and ignition phenomena of a single methanol droplet in a hot stagnant air was conducted to clarify the validity of the numerical method. Then the numerical simulation of the ignition of a methanol droplet in hot air flow was carried out, and the envelope flame developed around a droplet in a hot airflow was predicted. The effects of evaporation on droplet deformation and the ones of deformation of a droplet on the combustion phenomena around a droplet were numerically studied.2002, International Symposium on Combustion Abstracts of Works-in-Progress Posters, 397, EnglishInternational conference proceedings
- 日本混相流学会, Sep. 2016, 混相流 = Japanese journal of multiphase flow, 30(3) (3), 327 - 329, JapaneseReport on the 41th Lecture Series on Numerical Simulations of Multiphase Flows
- B224 Effects of liquid-separation components on two-phase swirling flow in a steam separatorA downscaled model of a steam separator is used to understand characteristics of swirling flow from the viewpoint of the effects of flow restriction ring (FRR) which is installed in a drainage channel. Main conclusions obtained are as follows. (1) Carryunder performance, the weight percentage of entrained gas in the water leaving the separator, improves by narrowing the flow area in the drainage channel using the FRR because it becomes hard to exhaust the gas. On the other hand, (2) the ratio of the separated flow rate to the liquid flow rate may decrease because the liquid phase climbing over the 1st pick-off ring and scattered droplets increase. Therefore, (3) it is necessary to optimize the FRR design based on the gas-liquid separation performance and pressure-loss performance.The Japan Society of Mechanical Engineers, 07 Jun. 2015, National Symposium on Power and Energy Systems, 2015(20) (20), 239 - 240, Japanese
- 日本流体力学会, Dec. 2014, ながれ, 33(6) (6), 509 - 512, Japanese時空間フィルタ流速計による単一液滴に作用する界面せん断応力の評価[Refereed][Invited]Report scientific journal
- GS35 Reduction of the Velocity Slips by the Immersed Boundary-Lattice Boltzmann MethodWe verify the effectiveness of the two-relaxation-time (TRT) collision operator in reducing boundary slip computed by the immersed boundary-lattice Boltzmann method (IB-LBM). Rigorous analysis of the symmetric Poiseuille flows reveals that the relaxation time for the antisymmetric part controls the boundary velocity and the boundary slip velocity computed by the IB-LBM. In the simulation of the cylindrical Couette flows, the boundary slip caused by the use of the single relaxation time (SRT) model in the IB-LBM impairs the accuracy that the LBM intrinsically possesses. The IB-LBMs with the TRT exhibit second-order accuracy in space for both the direct forcing method and the implicit correction method.The Japan Society of Mechanical Engineers, 25 Oct. 2014, Fluids engineering conference ..., 2014, "GS35 - 1"-"GS35-2", Japanese
- 日本計算工学会, Jun. 2014, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 19, 6p, JapaneseThe Accuracy Analysis of Immersed Boundary-Lattice Boltzmann Methods with Two Relaxation Times
- The Japan Society of Mechanical Engineers, 18 Mar. 2014, 関西支部講演会講演論文集, 2014(89) (89), "8 - 11", Japanese807 Effects of Liquid Viscosity on Flows Inside and Outside an Air Diffuser Pipe
- The Japan Society of Mechanical Engineers, 18 Mar. 2014, 関西支部講演会講演論文集, 2014(89) (89), "8 - 27", Japanese823 Lift Force Acting on Single Bubbles in Linear Shear Flows : Part II: numerical simulation
- The Japan Society of Mechanical Engineers, 18 Mar. 2014, 関西支部講演会講演論文集, 2014(89) (89), "8 - 26", Japanese822 Lift Force Acting on Single Bubbles in Linear Shear Flows : Part I: Experiment
- B121 Study on bubbly flow in a four by four rod bundleAlthough area-averaged void fractions in subchannels have been measured frequently in literatures, distribution of local void fraction in a rod bundle have been rarely reported. Little is also known on bubble motion in a rod bundle. Distributions of local void fraction and bubble velocity in a 4x4 rod bundle were, therefore, measured using a conductance probe in this study. Liquid velocity was also measured using LDV. Experimental results showed that the distributions of the void fractions in the inner and side subchannels depend not only on lift force acting on bubbles but also on geometrical interaction between the bubble and the rod wall. The relative velocity between bubbles and liquid phase in the subchannel possesses non-uniform distribution over the cross-section. This is caused by increase in drag force acting on bubbles due to bubble deformation induced by interaction between the bubbles and the rod wall.The Japan Society of Mechanical Engineers, 20 Jun. 2012, National Symposium on Power and Energy Systems, 2012(17) (17), 61 - 62, Japanese
- The Japan Society of Mechanical Engineers, 19 Mar. 2011, 関西支部講演会講演論文集, 2011(86) (86), "5 - 26", Japanese526 Interface Tracking Simulation of Mass Transfer in Gas-Liquid Two-Phase Flows
- 16 Dec. 2009, 微粒化シンポジウム講演論文集 = Symposium (ILASS-Japan) on Atomization, 18, 113 - 117, JapaneseLarge Eddy Simulation of Turbulent Cavitation Flow in a Nozzle
- G105 Cavitating Flow in a T-shape ElbowWater is more liable to evaporate than oils since its saturated vapor pressure is higher than the ones of oils. Therefore it is important to prevent erosion due to cavitation bubbles in hydraulic devices using water. In our previous study, we reported that erosion at elbow of pipeline can be reduced by using T-shape elbow. However its mechanism has not been clarified yet. In the present study, we observed cavitating flows in T-shape elbows of different shapes using a digital and high-speed video cameras. The amount of cavity was evaluated from taking images. As a result we confirmed that (1) circulating flow is steadily formed when the length of cavity-trapping region L ≧ 22.5 mm. If L ≦ 15 mm, circulating flow is formed intermittently, or it is not formed, (2) The amount of cavitation bubbles in cavity-trapping region increases as L increases, and (3)there are two uses (a) T-shape elbows can be used to guide cavitation bubbles into the region, in which circulating flow is formed, for defending the downstream of pipeline. (b) Then the elbows can also be used to guide bubbles to the downstream so as to prevent erosion at the elbows.The Japan Society of Mechanical Engineers, 17 Nov. 2007, Fluids engineering conference ..., 2007, "G105 - 1"-"G105-4", Japanese
- The Japan Society of Mechanical Engineers, 17 Nov. 2005, The Computational Mechanics Conference, 2005(18) (18), 805 - 806, Japanese2504 Application of Cahn-Hilliard Equation to the Evaluation of Surface Tension Force
- 2005, IEEE Trans.on Nuclear Science, 52(1),295-298, EnglishFlow Visualization of Segregation Process in a Fluidized-Bed by Neutron Radiography[Refereed]Others
- 2004, 日本混相流学会年会講演会講演論文集, 2004改良SCAによる流体粒子の界面追跡計算
- The Japan Society of Mechanical Engineers, 22 Nov. 2003, The Computational Mechanics Conference, 2003(16) (16), 111 - 112, JapaneseInterface Tracking Method based on Simplified Interface Reconstruction Method
- 2003, 日本混相流学会年会講演会講演論文集, 2003微粒化ノズル内キャビテーション流れと液体噴流の微粒化
- 2003, 日本混相流学会年会講演会講演論文集, 2003液滴・噴霧燃焼の数値シミュレーション
- 2002, 日本機械学会関西学生会卒業研究発表講演会講演前刷集, 2002界面追跡法の改良 新しい界面移流スキームの提案
- Contributor, 第１章, 化学工学会 関東支部, Jan. 2024, Japanese, ISBN: 4866938943化学工学系流体シミュレーションの最前線 ―基礎・実践・将来展望― (最近の化学工学 72)
- 朝倉書店, Apr. 2020, Japanese, ISBN: 4254237952流体力学 (機械工学基礎課程)
- Others, Chaps 1 and 2, World Scientific Publishing, May 2018, English, ISBN: 9789813229440Encyclopedia of Two-Phase Heat Transfer and Flow III: Macro and Micro Flow Boiling and Numerical Modeling FundamentalsScholarly book
- 第90回化学工学会年会, Mar. 2025, Japanese狭矩形容器内気泡流に及ぼす微細粒子及び界面活性剤の影響Oral presentation
- 38th CFD Symposium, Dec. 2024, JapaneseNumerical study of the motion of single bubble rising between parallel platesOral presentation
- 38th CFD Symposium, Dec. 2024, JapaneseSingle bubbles rising through stagnant liquid between thin gap cellsOral presentation
- 日本流体力学会年会2024, Sep. 2024, Japanese狭平板間静止液中単一気泡の分裂に関する研究Oral presentation
- 日本流体力学会年会2024, Sep. 2024, Japanese鉛直細円柱群内を上昇する気泡の形状と終端速度
- 日本機械学会年次大会, Sep. 2024, Japanese円管内旋回流による油水および固液分離に関する研究Poster presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese停滞水条件における3×3ロッドバンドル内での界面摩擦Oral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese鉛直円管内旋回環状流内体積率及び圧力損失の一次元三流体モデルによる予測Oral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese堆積層内気液二相流の流動特性に関する研究Oral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese気泡塔内ボイド率に及ぼす初期液位依存性に関する研究Oral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese気泡塔内非均質気泡流におけるドリフトフラックスパラメータの検討Oral presentation
- 混相流シンポジウム2024, Sep. 2024, JapaneseExperimental analysis of bubble terminal velocity in fiber bundleOral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese鉛直円管内テイラー気泡の液膜厚さに加振が及ぼす影響に関する研究Poster presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese平板間静止液中単一気泡の形状及び上昇速度に関する研究Poster presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese鉛直細円柱群内の気泡の運動に関する研究Poster presentation
- 混相流シンポジウム2024, Sep. 2024, Japaneseフラッディング状態での鉛直管内流動特性に対する管径の影響Oral presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese微細流路内テイラー気泡の形状に及ぼす界面活性剤の影響Poster presentation
- 混相流シンポジウム2024, Sep. 2024, Japanese平板間静止液中を上昇する単一気泡の形状及び抗力係数Oral presentation
- 第67回理論応用力学講演会, Sep. 2024, Japanese正方形マイクロチャネル内テイラー流の圧力損失と気泡速度に関する研究Oral presentation
- 第37回数値流体力学シンポジウム, Dec. 2023, Japanese脳動脈瘤内流れの血行力学パラメータの数値予測と機械学習による破裂リスク予測可能性の検討Oral presentation
- IUTAM Symposium on Dynamics and Interface Phenomena of Bubbles and Droplets at Multiple Scales, Dec. 2023, EnglishSurface Coverage of Bubbles with Surfactant or Particles[Invited]Oral presentation
- JSFM Annual Meeting 2023, Sep. 2023, EnglishEffects of viscosity ratio on lift force acting on a spherical dropOral presentation
- Multiphase Flow Symposium 2023, Aug. 2023, JapaneseStudy of surfactant adsorption on the surface of bubbles in a micro-channelOral presentation
- Multiphase Flow Symposium 2023, Aug. 2023, JapaneseMeasurement of drag coefficient of particle-attached bubbles generated by using micro-channelPoster presentation
- Multiphase Flow Symposium 2023, Aug. 2023, JapaneseEffect of bend curvature on void fraction of gas-liquid two-phase flow in a U-shaped bendPoster presentation
- Multiphase Flow Symposium 2023, Aug. 2023, JapaneseEffects of surfactant on drag and interfacial vorticity of spherical bubbleOral presentation
- Multiphase Flow Symposium 2023, Aug. 2023, JapaneseEffects of pipe diameter on interfacial and wall friction factors of swirling annular flows in a vertical pipeOral presentation
- ASME-JSME-KSME Fluids Engineering Division, AJKFED 2023, Jul. 2023, EnglishEffects of Fine Particles and Surfactant on Bubbly Flows in Narrow Rectangular ColumnOral presentation
- 11th International Conference on Multiphase Flow, ICMF-2023, Apr. 2023, EnglishLift Correlations of Ellipsoidal Bubbles in Low and High Viscosity Liquids[Invited]Keynote oral presentation
- 日本機械学会関西支部第98期定時総会講演会, Mar. 2023, Japanese中空糸膜を有する塔内気泡流に関する研究Oral presentation
- ANS Winter Meeting 2022, Nov. 2022, EnglishEffects of Upper and Lower Pipe Ends on Interfacial and Wall Friction Factors under Counter-Current Flow Limitation in a Vertical PipeOral presentation
- ANS Winter Meeting 2022, Nov. 2022, EnglishEffects of Liquid Viscosity on Friction Factors of Gas-Liquid Swirling Annular Flows in a Vertical PipeOral presentation
- 1st European-American-Japanese Two-Phase Flow Group Meeting (EAJTPFGM22), Oct. 2022, EnglishFragmentation of Liquid Drop Falling through Miscible Liquid due to Rayleigh-Taylor InstabilityNominated symposium
- 1st European-American-Japanese Two-Phase Flow Group Meeting (EAJTPFGM22), Oct. 2022, EnglishBubbly Flows in a Column with Submerged Hollow Fiber MembranesOral presentation
- 日本流体力学会年会2022, Sep. 2022, JapaneseEffects of microbubbles on removal of highly-viscous oil adhering to channel wallOral presentation
- 4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), Sep. 2022, EnglishPressure Drop of Single Bubble in Taylor Flows through Square MicrochannelsOral presentation
- 4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), Sep. 2022, EnglishBubbly Flows in a Vertical Pipe with Horizontal OscillationPoster presentation
- 混相流シンポジウム2022, Aug. 2022, JapanesePressure drop of single bubble in Taylor flows through square microchannelsOral presentation
- 混相流シンポジウム2022, Aug. 2022, JapaneseBreakup of single two-dimensional bubbles in stagnant waterOral presentation
- 混相流シンポジウム2022, Aug. 2022, JapaneseEffects of upper and lower pipe ends on interfacial and wall friction factors under counter-current flow limitation in a vertical pipeOral presentation
- 混相流シンポジウム2022, Aug. 2022, JapaneseEffects of swirl intensity and liquid viscosity on interfacial and wall friction factors of annular flows in a vertical pipeOral presentation
- 日本流体力学会年会2021, Sep. 2021, JapaneseNumerical Simulations of Single Contaminated Spherical DropsOral presentation
- 混相流シンポジウム2021, Aug. 2021, Japanese堆積層内における気液二相流に関する研究Oral presentation
- 混相流シンポジウム2021, Aug. 2021, Japanese振動を伴う鉛直円管内の気液二相流動特性に関する研究
- 混相流シンポジウム2021, Aug. 2021, Japanese鉛直円管内気液二相旋回流の界面および壁面摩擦係数に及ぼす旋回強度の影響
- 混相流シンポジウム2021, Aug. 2021, Japanese鉛直サーペンタイン管内気液二相流のボイド率及び液膜厚さ
- 混相流シンポジウム2021, Aug. 2021, Japanese垂直U字管内気液二相流のボイド率に関する研究
- 混相流シンポジウム2021, Aug. 2021, Japanese気泡流による中空糸膜の汚れ除去と揺動に関する研究
- 混相流シンポジウム2021, Aug. 2021, Japanese気泡塔内平均及び局所ボイド率の初期液位依存性に関する研究
- 混相流シンポジウム2020, Aug. 2020, Japanese鉛直円管内気液二相流に及ぼす管加速度の影響に関する研究Oral presentation
- 混相流シンポジウム2020, Aug. 2020, Japanese鉛直円管内旋回環状流の界面及び壁面摩擦係数に及ぼす液相粘度の影響Oral presentation
- 混相流シンポジウム2020, Aug. 2020, Japanese気泡群による液相中粒子の輸送能力評価Oral presentation
- 混相流シンポジウム2020, Aug. 2020, Japanese鉛直 U 字管内気液二相流の流動特性に関する研究Oral presentation
- 混相流シンポジウム2020, Aug. 2020, Japanese鉛直円管内アルカリ溶液中二酸化炭素気泡の化学吸収に関する研究Oral presentation
- 日本機械学会関西支部第95期定時総会講演会, Mar. 2020, JapaneseNumerical Simulations of Flows in Cerebral Aneurysms Using the Lattice Boltzmann MethodOral presentation
- 2019 Annual Meeting of the Japanese Society of Fluid Mechanics, Sep. 2019, Japanese, 日本流体力学会, 調布, Domestic conferenceEffects of Surfactant on Taylor Flows in a MicrochannelOral presentation
- Multiphase Flow Symposium 2019, Aug. 2019, Japanese, 日本混相流学会, 福岡, Domestic conferenceInterfacial and wall friction factors for gas-liquid counter-current flow in vertical pipesOral presentation
- Multiphase Flow Symposium 2019, Aug. 2019, Japanese, 日本混相流学会, 福岡, Domestic conferenceInterfacial and wall friction factors of a swirling annular flowOral presentation
- Annual European Rheology Conference 2019 (AERC 2019), Apr. 2019, English, Portorož, Slovenia, International conferenceThree-Dimensional Flow Characteristics around a Bulge Structure in a Cavity Swept by a Viscoelastic FluidsOral presentation
- 第20回気液固分散工学サロン, Mar. 2019, Japanese, 芝浦工業大学, Domestic conference管路内気泡・液滴の運動に及ぼす界面活性剤の影響[Invited]Invited oral presentation
- 第95期日本機械学会流体工学部門講演会, Nov. 2018, Japanese, 日本機械学会, Muroran, Domestic conference単一液滴に作用する力の実験的分析Poster presentation
- 日本流体力学会年会2018, Sep. 2018, Japanese, 大阪大学, Domestic conference可溶性界面活性剤により汚染された球形液滴の数値シミュレーションOral presentation
- 混相流シンポジウム2018, Aug. 2018, Japanese, 仙台, Domestic conference上端シャープエッジ鉛直管における気液二相対向流の界面及び壁面摩擦係数Oral presentation
- 混相流シンポジウム2018, Aug. 2018, Japanese, 仙台, Domestic conference鉛直円管内単一二酸化炭素気泡の物質移動に及ぼすアルコールと電解質の相互作用の影響Oral presentation
- 混相流シンポジウム2018, Aug. 2018, Japanese, 仙台, Domestic conferenceU字管内気液二相流の圧力損失に及ぼす液相粘度の影響Oral presentation
- 混相流シンポジウム2017, Aug. 2017, Japanese, 東京, Domestic conference気泡による微細粒子輸送に関する研究Oral presentation
- 混相流シンポジウム2017, Aug. 2017, Japanese, 東京, Domestic conference鉛直円管内旋回気液二相流の圧力損失に関する研究Oral presentation
- 混相流シンポジウム2017, Aug. 2017, Japanese, 東京, Domestic conferenceU字管内気液二相流の圧力損失に関する研究Oral presentation
- International Conference on Numerical Methods in Multiphase Flow, Jun. 2017, English, Tokyo, International conferenceNumerical Simulation of Contaminated Bubbles and Drops Using Level Set Method (Keynote Lecture)Keynote oral presentation
- 日本機械学会研究分科会RC270第3回分科会, Dec. 2016, Japanese, 日本機械学会, Tokyo, Domestic conference二相流数値計算検証のための実験計測Nominated symposium
- 第22回流動化・粒子プロセッシングシンポジウム, Dec. 2016, Japanese, Domestic conference気泡と液液のシミュレーションとモデリング（招待講演）Oral presentation
- 第94期日本機械学会流体工学部門講演会, Nov. 2016, Japanese, Domestic conference時空間フィルタ流速計による界面活性剤の吸着を伴う液滴の測定Oral presentation
- 混相流シンポジウム2016, Aug. 2016, Japanese, Domestic conference塔径及び初期液位が気泡塔内平均ボイド率に及ぼす影響Oral presentation
- 混相流シンポジウム2016, Aug. 2016, Japanese, Domestic conference静止液中単一気泡の形状に及ぼす界面活性剤の影響に関する研究Oral presentation
- 混相流シンポジウム2016, Aug. 2016, Japanese, Domestic conferenceShapes of single bubbles in infinite stagnant liquids contaminated with surfactantOral presentation
- 混相流シンポジウム2016, Aug. 2016, Japanese, Domestic conference鉛直円管内電解質水溶液中単一二酸化炭素気泡の物質移動に関する研究Oral presentation
- 混相流シンポジウム2016, Aug. 2016, Japanese, Domestic conferenceU字管内気液二相流の圧力損失に関する研究Oral presentation
- 日本機械学会関西支部第91期定時総会講演会, pp. 129-132, Mar. 2016, Japanese, 大阪, Domestic conference散気管内外の流れに散気孔の周方向角度が及ぼす影響Oral presentation
- 第29回数値流体力学シンポジウム, Dec. 2015, Japanese, 九州大学筑紫キャンパス, Domestic conference埋め込み境界－熱流動格子ボルツマン法における熱流束境界条件の精度に及ぼす二緩和時間衝突則の影響Oral presentation
- American Physical Society 68th Annual DFD Meeting, Nov. 2015, English, Boston,Massachusetts, U.S.A., International conferenceReduction of the Temperature Jump in the Immersed Boundary-Thermal Lattice Boltzmann MethodOral presentation
- 日本機械学会研究分科会RC263第6回分科会, Sep. 2015, Japanese, 日本機械学会, Tokyo, Domestic conference境界適合型時空間フィルタ流速計と界面活性剤濃度評価の試みNominated symposium
- 日本流体力学会年会2015, Sep. 2015, Japanese, 日本流体力学会, Tokyo, Domestic conferenceStudy on adsorption of surfactant at interface of a spherical dropOral presentation
- 混相流シンポジウム2015, Aug. 2015, Japanese, 高知工科大学, Domestic conference二緩和時間衝突則に基づく埋め込み境界法を適用した熱流動格子ボルツマン法Oral presentation
- 混相流シンポジウム2015, Aug. 2015, Japanese, Kochi, Domestic conferenceEvaluation of Marangoni Stress Acting on a Single Contaminated Spherical DropOral presentation
- 混相流シンポジウム2015, Aug. 2015, Japanese, 高知, Domestic conference一様せん断流中単一気泡に働く揚力に関する研究Oral presentation
- 混相流シンポジウム2015, Aug. 2015, Japanese, 高知, Domestic conferenceサブクール水中における蒸気凝縮音に関する研究Oral presentation
- 第20回動力・エネルギー技術シンポジウム, Jun. 2015, Japanese, 日本機械学会動力エネルギーシステム部門, Sendai, Domestic conferenceEffects of liquid-separation components on two-phase swirling flow in a steam separatorOral presentation
- 日本原子力学会 春の大会 2015, Mar. 2015, Japanese, 茨城, Domestic conference冷却材喪失事故時の格納容器内温度シミュレーションモデルの検証；（2）空気及び蒸気吹込み実験Oral presentation
- 日本機械学会流体工学部門講演会, Oct. 2014, Japanese, 富山, Domestic conferenceReduction of the velocity slips by the immersed boundary-lattice Boltzmann methodOral presentation
- 日本流体力学会年会2014, Sep. 2014, Japanese, 日本流体力学会, 宮城県仙台市, Domestic conference時空間フィルタ流速計による単一液滴に作用する界面せん断応力の評価Oral presentation
- 理論応用力学講演会, Sep. 2014, Japanese, 日本学術会議, 東京都, Domestic conference時空間フィルタ流速計による界面近傍速度測定Oral presentation
- 混相流シンポジウム2014, E151, USB Memory (2 pages), Jul. 2014, Japanese, 札幌, Domestic conference非一様電場におけるオリフィスからの気泡成長Oral presentation
- 混相流シンポジウム2014, A311, USB Memory (2 pages), Jul. 2014, Japanese, 札幌, Domestic conference固体壁に付着した液滴に及ぼす界面活性剤の影響に関する研究Oral presentation
- 混相流シンポジウム2014, B331, USB Memory (2 pages), Jul. 2014, Japanese, 札幌, Domestic conference汚れ系における気泡の界面追跡計算と物質移動Keynote oral presentation
- 混相流シンポジウム2014, A311, USB Memory (2 pages), Jul. 2014, Japanese, Domestic conferenceスラリー気泡塔内平均ボイド率に及ぼす初期液位の影響Oral presentation
- 混相流シンポジウム2014, B232, USB Memory (2 pages), Jul. 2014, Japanese, 札幌, Domestic conferenceスラリー気泡塔における気泡合体に粒子径が及ぼす影響Oral presentation
- 混相流シンポジウム2014, B223, USB Memory (2 pages), Jul. 2014, Japanese, 札幌, Domestic conferenceU字ベンドにおける空気水系気液二相流の圧力損失に関する研究Oral presentation
- 10th International Congress on Membranes and Membrane Processes (ICOM2014), Jul. 2014, English, Suzhou, China, International conferenceNumerical Study of Concentrated Emulsion Flow Through a Membrane Pore in Oil/Water SeparationOral presentation
- 日本機械学会関西支部定時総会・講演会2014, Mar. 2014, Japanese, 大阪府立大学, Domestic conference散気管内外の流れに及ぼす液相粘度の影響Oral presentation
- 日本機械学会関西支部定時総会・講演会2014, Mar. 2014, Japanese, 大阪府立大学, Domestic conference一様せん断流中単一気泡に働く揚力に関する研究 (第2 報 数値計算)Oral presentation
- 日本機械学会 関西支部第89期定時総会講演会, Mar. 2014, Japanese, 日本機械学会関西支部, 大阪, Domestic conference一様せん断流中単一気泡に働く揚力に関する研究(第 1 報 実験)Oral presentation
- 膜シンポジウム2013, Nov. 2013, Japanese, 日本膜学会, 京都府立医科大学 （京都）, Domestic conference膜分離プロセスにおける流体挙動のモデリングとシミュレーションOral presentation
- 混相流シンポジウム2013, Aug. 2013, Japanese, 日本混相流学会, 長野, Domestic conference散気管内外の流れに液相粘性が及ぼす影響に関する研究Oral presentation
- 混相流シンポジウム2013, Aug. 2013, Japanese, 日本混相流学会, 長野, Domestic conference鉛直円管内CO2気泡周りの濃度分布計測Oral presentation
- 第62回理論応用力学講演会, Mar. 2013, Japanese, 東京工業大学, Domestic conference粘性力及び表面張力の評価法が界面運動の数値予測に及ぼす影響Oral presentation
- JSMF Annual Meeting 2012, Aug. 2012, Japanese, 日本混相流学会, Kashiwa, Domestic conferenceEffects of surfactant on the lift force acting on bubbles in linear shear flowsOral presentation
- JSMF Annual Meeting 2012, Aug. 2012, Japanese, 日本混相流学会, Kashiwa, Domestic conferenceReduction of boundary slip from the immersed boundary-lattice Boltzmann method by two-relaxation-timeOral presentation
- JSMF Annual Meeting 2012, Aug. 2012, Japanese, 日本混相流学会, Kashiwa, Domestic conferenceImmersed Boundary-Finite Difference Lattice Boltzmann Method Using Two Relaxation TimesOral presentation
- The 17th National Symposium on Power and Energy Systems (SPES 2012), Jun. 2012, Japanese, 日本機械学会動力・エネルギー部門, Fukuoka, Domestic conferenceStudy on bubbly flow in a four by four rod bundleOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 京都, Domestic conferenceBasic study of flow inside a diffuser for membrane bioreactorOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 京都, Domestic conferenceDissolution process of a high Schmidt and low Reynolds numbersOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 日本混相流学会, Kyoto, Domestic conference空間フィルタ流速計による気泡速度の測定Oral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 日本混相流学会, 京都, Domestic conferenceInterface tracking simulation of bubbles with adsorption and desorption of soluble surfactantOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 京都, Domestic conferenceEffects of particle size and concentration on bubble coalescence in slurry bubble columnOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 京都, Domestic conferenceCountercurrent flow limitation at the upper end of PWR pressurizer surge lineOral presentation
- JSMF Annual Meeting 2011, Aug. 2011, Japanese, 日本混相流学会, Kyoto, Domestic conference4x4ロッドバンドル内気液二相気泡流に関する研究Oral presentation
- 日本機械学会関西支部 第86期定時総会講演会, Mar. 2011, Japanese, 日本機械学会関西支部, 京都, Domestic conference界面追跡法に基づく気液間物質輸送の数値計算Oral presentation
- 14th Organized Multiphase Flow Forum 2010, Nov. 2010, Japanese, The Japan Society for Multiphase Flow, Sapporo, Hokkaido, Domestic conferenceAdvances in Interface Tracking Method for Hear and Mass Transfers[Invited]Invited oral presentation
- JSMF Annual Meeting 2010, Jul. 2010, Japanese, Hamamatsu, Domestic conferenceNumerical simulation of bubbly flow in slurry using multi-fluid modelOral presentation
- 日本混相流学会年会講演会2010, Jul. 2010, Japanese, 静岡, Domestic conference汚泥減圧浮上濃縮装置の開発Oral presentation
- JSMF Annual Meeting 2010, Jul. 2010, Japanese, Hamamatsu, Domestic conferenceA correlation of terminal velocity for Taylor drops in vertical pipesOral presentation
- 18th Symposium on Atomization (ILASS-Japan), Dec. 2009, Japanese, 日本液体微粒化学会, Kyushu University, Domestic conferenceLarge Eddy Simulation of Cavitating Turbulent Flow in a NozzleOral presentation
- JSMF Annual Meeting 2009, Aug. 2009, Japanese, 日本混相流学会, Kumamoto, Domestic conferencePressure Drops in Rod Bundle with Partial Length RodsOral presentation
- 日本混相流学会年会講演会2009, pp. 224-225, Aug. 2009, Japanese, Domestic conference水平管内マイクロバブル乱流の摩擦圧力損失特性に関する研究Oral presentation
- JSMF Annual Meeting 2009, Aug. 2009, Japanese, 日本混相流学会, Kumamoto, Domestic conferenceHeat Transfer Enhancement by Air Bubble Rising through Thermally Stratified LayerOral presentation
- 日本混相流学会年会講演会2009, pp. 152-153, Aug. 2009, Japanese, 熊本, Domestic conference気相体積率に基づく旋回気液二相流の流動様式判別Oral presentation
- JSMF Annual Meeting 2009, Aug. 2009, Japanese, 日本混相流学会, Kumamoto, Domestic conferenceTerminal velocities of single large drops rising through a vertical pipeOral presentation
- 日本高専学会第15回年会・講演会, Aug. 2009, Japanese, 愛知, Domestic conferenceサイホンを利用した汚泥減圧濃縮装置の開発Oral presentation
- 日本混相流学会年会講演会2008, pp. 244-245, Jun. 2008, Japanese, 会津, Domestic conferenceT字形のエルボを流動するキャビテーションに関する研究Oral presentation
- 日本機械学会流体工学部門講演会, CD-ROM (4 pages), Nov. 2007, Japanese, 日本機械学会, 広島, Domestic conferenceT字形エルボにおけるキャビテーションの流動Oral presentation
- 日本混相流学会年会講演会2007, pp. 152-153, Jun. 2007, Japanese, 日本混相流学会, 北海道, Domestic conference鉛直管内旋回気液二相流の流動様式と旋回長さに関する研究Oral presentation
- 日本流体力学会第20回数値流体力学シンポジウム, CO-ROM (6 pages), Dec. 2006, Japanese, 日本流体力学会, 名古屋, Domestic conferenceフェーズフィールド界面追跡法による二相流数値シミュレーションOral presentation
- JSMF Annual Meeting 2006, Aug. 2006, Japanese, Kanazawa, Domestic conferenceStudy on Lift Force Acting on Single Drops in Linear Shear FlowOral presentation
- 日本計算工学会第11回計算工学講演会, pp. 415-416, Jun. 2006, Japanese, 日本計算工学会, 大阪, Domestic conference二相流シミュレーションの界面移流・再構成計算に対するカーン‐ヒリヤード方程式の適用性の検討Oral presentation
- 日本機械学会第18回計算力学講演会, pp. 805-806, 2005, Japanese, 日本機械学会, 筑波, Domestic conference表面張力評価へのカーン‐ヒリヤード方程式の応用Oral presentation
- 日本混相流学会年会講演会, 2004, Japanese, 日本混相流学会, 岡山大学, Domestic conference改良SCA法による液体粒子の界面追跡計算Oral presentation
- 日本混相流学会年会講演会, 2003, Japanese, 日本混相流学会, 大阪大学, Domestic conference微粒化ノズル内キャビテーション流れと液体噴流の微粒化Oral presentation
- 日本機械学会第16回計算力学講演会, 2003, Japanese, 日本機械学会計算力学部門, 神戸大学工学部, Domestic conference簡素化界面再構築法に基づく界面追跡法Oral presentation
- 産学官技術フォーラム’03, 2003, Japanese, 神戸市立工業高等専門学校, 神戸商工会議所, 神戸市産業振興センター, Domestic conference界面追跡法による気液二相流数値予測の試みPoster presentation
- 日本混相流学会年会講演会, 2003, Japanese, 日本混相流学会, 大阪大学, Domestic conference液滴・噴霧燃焼の数値シミュレーションOral presentation
- Society for Chemical Engineers, JapanMar. 2024 - Present
- 日本流体力学会May 2018 - Present
- 日本高専学会Jul. 2009 - Jun. 2010
- 日本混相流学会
- 日本機械学会
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, Apr. 2024 - Mar. 2027Modeling of lift force acting on contaminated deformed bubbles in terms of surface vorticity and its application to bubbly flows
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kobe University, Apr. 2023 - Mar. 2026, CoinvestigatorDevelopment of numerical method for bubbly flows inside and outside dense vertical structures
- 兵庫県, 成長産業育成のための研究開発支援事業, 可能性調査・研究, 森合精機・神戸大学, Sep. 2024 - Mar. 2025, Others洗浄機械における旋回流を利用した 油水分離促進技術の可能性調査
- 関西エネルギー・リサイクル科学研究振興財団, 研究助成, 神戸大学, Apr. 2024 - Mar. 2025, Principal investigator狭隘流路内を運動する気泡の実用的抗力モデルの開発
- JKA, 研究補助, 個別研究, Apr. 2023 - Mar. 2024, Principal investigator粒子に覆われ安定化された気泡の掩蔽状態よ揚力機構の解明
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), Kobe University, 01 Apr. 2020 - 31 Mar. 2023Development of a Surfactant Separator by Using Taylor Flows in Microchannels本研究課題では，界面活性剤を含む微細流路内テイラー流の特性を解明するとともに，テイラー流を利用した高効率界面活性剤分離技術の基盤を確立することを目的として各要素研究を推進している．微細流路内テイラー気泡の形成に関して，これまでに界面活性剤の効果により気泡長さが増加する形成モードと減少する形成モードがあることを明らかにしてきた．2021年度は，気液体積流束の範囲を広くとって実験を行い，幅500マイクロメートルの微細流路内での形成モードの流量配分依存性について詳しく調べたところ，本条件の範囲においては，ほとんどの条件で増加のモードであることを明らかにした．その理由について，吸脱着および流れのタイムスケールからなる八田数と，マンランゴニ応力と粘性力のオーダーからなるマランゴニ数をもとにモード遷移の主要因を検討した．界面活性剤分離器開発について，種々の界面活性剤濃度で分離実験を行った．その結果，テイラー流として微細流路を通過させることによって，液相の初期界面活性剤濃度が臨界ミセル濃度前後の広い範囲で半分程度に低減できることを明らかにした．一方，本実験結果から，微細流路内の吸着状態を検討し，微細流路と分離槽における分離過程について検討した．また，微細流路通過後の分離槽における気泡挙動が分離器設計上重要であるため，気泡力学的検討を前年度に引き続いてさらに推進し，揚力や界面活性剤が及ぼす気泡運動への影響への理解を深化させた．
- カシオ科学振興財団, 研究協賛, Dec. 2021 - Nov. 2022, Principal investigator粒子付着気泡生成器開発とその介在物除去技術への展開
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kansai University, 01 Apr. 2019 - 31 Mar. 2022Investigation and modeling of adsorption-desorption kinetics of surfactants at interface with deformation and oscillationBubbles and drops in a contaminated system can be found in many industrial applications and natural phenomena. The contaminants such as surface-active agents (surfactant) adsorb on the interface of bubbles or drops and change mass, momentum, and heat transfer characteristics. Although there are lots of knowledge and models of the adsorption-desorption kinetics for quiescent systems, those have rarely been validated for a moving interface due to the lack of experimental data. Hence, we experimentally investigated local viscous stress, pressure, and surfactant concentration at the moving interface of drops falling in a stagnant liquid containing surfactant based on the velocity distribution measured by spatiotemporal filter velocimetry (SFV). The SFV was extended to generalized coordinate systems to evaluate adsorption characteristics of deformed drops. We discussed the adsorption-desorption kinetics and the influence of the adsorption on the fluid force acting on the drop.
- マツダ財団, マツダ研究助成, Nov. 2020 - Mar. 2022, Principal investigator強制振動管内気液二相流に及ぼす慣性力の影響の解明
- 科学研究費補助金／基盤研究(A), Apr. 2018 - Mar. 2022Competitive research funding
- (財)関西エネルギー・リサイクル科学研究振興財団, 研究助成：エネルギー・リサイクル分野, Apr. 2019 - Mar. 2020, Principal investigator海底ガス資源回収用垂直管に生じる振動管内気液二相流動に関する基礎研究
- 学術研究助成基金助成金／基盤研究(C), Apr. 2017 - Mar. 2020Competitive research funding
- 学術研究助成基金助成金／基盤研究(C), Apr. 2017 - Mar. 2020, Principal investigatorCompetitive research funding
- Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kobe University, 01 Apr. 2016 - 31 Mar. 2019Experimental investigation and modeling of adsorption of surfactants on a moving interfaceNumerical simulations of contaminated bubbles or drops adopt a model of adsorption-desorption kinetics developed for quiescent systems. However, the model has rarely been validated due to the lack of experimental data of surfactant concentration at a moving interface. Hence, we experimentally investigated surfactant concentration at the moving interface of a spherical drop falling in a stagnant liquid containing surfactant based on the velocity distribution measured by spatiotemporal filter velocimetry (SFV). The applicability of the Frumkin-Levich model to a drop falling in a contaminated system was examined based on the measured data. The result showed that the evaluation of surfactant concentration using SFV is of great use in understanding adsorption-desorption kinetics at an interface in a contaminated system and in validation of adsorption and desorption models. The Frumkin-Levich model is not applicable to a moving interface, whereas it is applicable to an immobile interface.
- 科学研究費一部基金／基盤研究(B), Apr. 2015 - Mar. 2018Competitive research funding
- 伊藤忠兵衛基金, 学術研究事業助成, Apr. 2015 - Mar. 2016, Principal investigator気泡を用いたろ過膜洗浄の計測及び数値シミュレーョンに基づく洗浄速度モデリングに関する研究
- 学術研究助成基金助成金／若手研究(B), Apr. 2013 - Mar. 2015, Principal investigatorCompetitive research funding
- (財)関西エネルギー・リサイクル科学研究振興財団, 研究助成：エネルギー・リサイクル分野, Apr. 2012 - Mar. 2013, Principal investigator天然ガス液体燃料製造工程において触媒粒子が合成ガス気泡合一に及ぼす影響の解明
- 科学研究費補助金／若手研究(B), Apr. 2011 - Mar. 2013, Principal investigatorCompetitive research funding
- (財)ひょうご科学技術協会, 学術研究助成事業, Apr. 2011 - Mar. 2012, Principal investigator水質汚染環境下気泡の運動に対する汚染物質の影響のモデル化
- (財)油空圧機器技術振興財団, 研究助成事業, Apr. 2009 - Mar. 2010, Principal investigator配管内キャビテーション損傷対策のための高安全特殊エルボの開発