冨山 明男 | ![]() |
トミヤマ アキオ | |
大学院工学研究科 機械工学専攻 | |
教授 | |
機械工学関係 |
2017年08月 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
日本国その他の賞
2014年12月 15th International Topical Meeting on Nuclear Reactor Thermalhydraulics (NURETH-15), Best Paper Award, Concendation Experiments for Counter-Current Flow Limitation at Lower End of an Invertied U-Tube
日本国国際学会・会議・シンポジウム等の賞
2013年05月 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 Bundle
The “best” poster based on the structure of the presentation (visual quality), イタリア共和国国際学会・会議・シンポジウム等の賞
2013年04月 日本機械学会, 2012年度 日本機械学会賞(論文), フォトブリーチング分子タグ法による乱れエネルギ収支の評価
日本機械学会論文集, 77巻, 784号, B編(2011年12月), 日本国国内学会・会議・シンポジウム等の賞
2005年08月 日本混相流学会, 2004年度日本混相流学会賞 論文賞, 鉛直円管内低濃度固気二相流の乱流変調に及ぼす相間相対速度の影響
2004年03月 日本原子力学会, 第36回日本原子力学会賞 論文賞, Shape and Rising Velocities of Single Bubble risingnthrough an Inner Subchannel
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研究論文(国際会議プロシーディングス)
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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.
2019年02月, World neurosurgery, 122, e1439-e1448 - e1448, 英語, 国際誌[査読有り]
研究論文(学術雑誌)
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.
2019年01月, World neurosurgery, 121, e287-e295 - e295, 英語, 国際誌[査読有り]
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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., 2018年09月01日, Experimental Thermal and Fluid Science, 96, 460 - 469, 英語[査読有り]
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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, 2018年04月15日, Nuclear Engineering and Design, 330, 97 - 105, 英語[査読有り]
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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, 2018年03月10日, International Journal for Numerical Methods in Fluids, 86 (7), 454 - 490, 英語[査読有り]
研究論文(学術雑誌)
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, 2018年03月01日, Nuclear Engineering and Design, 328, 182 - 187, 英語[査読有り]
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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年, 化学工学論文集, 44 (1), 59 - 66, 日本語[査読有り]
研究論文(学術雑誌)
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, 2017年12月01日, International Journal of Multiphase Flow, 97, 157 - 167, 英語[査読有り]
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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, 2017年12月, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 115, 663 - 671, 英語[査読有り]
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研究論文(国際会議プロシーディングス)
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, 2017年12月, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 89, 90 - 97, 英語[査読有り]
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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, 2017年11月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 96, 113 - 122, 英語[査読有り]
研究論文(学術雑誌)
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, 2017年10月, NUCLEAR ENGINEERING AND DESIGN, 322, 360 - 367, 英語[査読有り]
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We previously developed a one- dimensional (1-D) computation method with parameters adjusted from CCFL (countercurrent flow limitation) data in hot leg and pressurizer surge line models to generalize the prediction method for CCFL in nearly horizontal pipes. In the 1-D computation method, the constant value for the interfacial friction coefficient of fi = 0.03 was used. On the other hand, many correlations for the interfacial friction coefficient in horizontal and inclined pipes have been proposed. In this study, therefore, we carried out 1-D computations for CCFL in nearly horizontal pipes with the diameter of D = 0.03-0.75 m and the length to diameter ratio of L/D = 4.5-63 by using some selected correlations for the interfacial friction coefficient, which are a function of the gas or liquid Reynolds number. As a result, we confirmed that the correlation of the interfacial friction coefficient in terms of the Reynolds number cannot be used for large Reynolds numbers but fi = 0.03 can be used for the wide range of diameters. To improve the correlation with the gas or liquid Reynolds number, we proposed a modified correlation. (C) 2017 Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE SA, 2017年08月, NUCLEAR ENGINEERING AND DESIGN, 320 (15), 418 - 426, 英語[査読有り]
研究論文(学術雑誌)
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.
日本混相流学会, 2017年06月, 混相流, 31 (1), 37 - 46, 日本語[査読有り]
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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, 2017年05月, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 108 (Part B), 1991 - 2001, 英語[査読有り]
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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, 2017年04月, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 82, 359 - 366, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
We proposed prediction methods for countercurrent flow limitation (CCFL) in horizontal and slightly inclined pipes with one- dimensional (1- D) computations and uncertainty of computed CCFL. In this study, we applied the proposed methods to a full-scale pressurizer surge line [ inclination angle theta = 0.6 deg, diameter D = 300 mm, and ratio of the length to the diameter (L/D) = 63] in a specific pressurized water reactor, performed 1-D computations and three-dimensional (3-D) numerical simulations, and found that uncertainties caused by effects of the diameter and fluid properties on CCFL were small. We also applied the proposed methods to experiments for hot-leg and surge line models (theta = 0 and 0.6 deg, D = 0.03 to 0.65 m, and L/D = 4.5 to 63) to generalize them, performed 1-D computations, and found that uncertainties caused by effects of theta and L on CCFL were large due to the setting error for theta and differences among experiments. This shows that a small-scale air-water experiment with the same theta and L/D as those in an actual plant is effective to reduce the uncertainty of CCFL prediction.
AMER NUCLEAR SOC, 2017年02月, NUCLEAR TECHNOLOGY, 197 (2), 140 - 157, 英語[査読有り]
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研究論文(学術雑誌)
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, 2016年11月, NUCLEAR ENGINEERING AND DESIGN, 308, 205 - 213, 英語[査読有り]
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研究論文(国際会議プロシーディングス)
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, 2016年09月, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 49 (9), 824 - 830, 英語[査読有り]
研究論文(学術雑誌)
[招待有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
Improvement of efficiency of a gaslift pump is required for lifting submarine resources economically. We propose a gaslift pump utilizing phase change of working fluid to improve the efficiency by avoiding air compression. A working fluid, which has a boiling point lower than surrounding temperature, is supplied as liquid to an evaporator near the bottom of a riser pipe through an adiabatic pipe. The working fluid boils at the evaporator due to heating from the surrounding liquid. The generated gas is injected into the riser pipe instead of compressed air and forms gas-liquid two-phase flow, by which the water is drawn from the bottom opening of the riser pipe. The working fluid is separated from the drawn water at the top of the pipe, and it flows into a cooler to supply the condensed liquid into the adiabatic pipe again. This pump needs the energy only to cool the working fluid, i.e. no energy is required for compressing gas. The feasibility of the pump is confirmed through the experiments using a prototype gaslift pump using a hydro-fluorocarbon as the working fluid. Prediction of the flow rate of drawn water is also carried out. (C) 2016 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2016年06月, APPLIED THERMAL ENGINEERING, 103, 1119 - 1125, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
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, 2016年04月, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 53 (4), 486 - 495, 英語[査読有り]
研究論文(学術雑誌)
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, 2016年04月, Experimental Thermal and Fluid Science, 72, 67 - 74, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
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, 2016年03月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 79, 23 - 30, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
Mass transfer from single CO2 Taylor bubbles in vertical minichannels was measured for various channel hydraulic diameters D-h. The effects of channel geometries on the mass transfer were also investigated by using square ducts and circular pipes. Bubble rising velocities, v(B), in the ducts were much faster than those in the pipes due to large liquid flow areas in the corners of the ducts. The values of mass transfer coefficients in the pipes were almost the same as those in the ducts, in spite of a large difference in v(B). Sherwood numbers, Sh(D), using D-h as a characteristic length, are well-correlated in terms of the Eotvos number. The proposed Sh(D) correlation can well predict a long-term dissolution process of a Taylor bubble.
WILEY-V C H VERLAG GMBH, 2015年11月, CHEMICAL ENGINEERING & TECHNOLOGY, 38 (11), 1925 - 1932, 英語[査読有り][招待有り]
研究論文(学術雑誌)
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, 2015年11月, CHEMICAL ENGINEERING & TECHNOLOGY, 38 (11), 1955 - 1964, 英語[査読有り][招待有り]
研究論文(学術雑誌)
One-dimensional (1D) sensitivity computations were carried out for air–water countercurrent flows in a 1=15-scale model of the hot leg and a 1=10-scale model of the pressurizer surge line in a pressurized water reactor (PWR) to generalize the prediction method for countercurrent flow limitation (CCFL) characteristics in slightly inclined pipes with elbows. In the 1D model, the wall friction coefficient fwG of single-phase gas flows was used. The interfacial drag coefficient of fi ¼ 0.03, an appropriate adjustment factor of NwL ¼ 6 for the wall friction coefficient fwL of single-phase liquid flows (NwG ¼ 1 for fwG of single-phase gas flows), and an appropriate adjustment factor of Nde ¼ 6 for the pressure loss coefficient ζe of elbows in single-phase flows were determined to give good agreement between the computed and measured CCFL characteristics. The adjusted factors were used to compute and then discuss effects of the inclination angle and diameter on CCFL characteristics.
American Society of Mechanical Engineers (ASME), 2015年10月01日, Journal of Nuclear Engineering and Radiation Science, 1 (4), 041009, 9 pages, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り][招待有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
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, 2015年09月, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 66, 197 - 205, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
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, 2015年06月, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 52 (6), 887 - 896, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
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, 2015年03月01日, Journal of Computational Multiphase Flows, 7 (1), 15 - 32, 英語[査読有り]
研究論文(学術雑誌)
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, 2015年03月, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 48 (3), 181 - 189, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Micro-bubbles are in use in many industrial fields such as water treatment, purification of lake water, chemical engineering, washing processes and housing equipment by virtues of their large interfacial area concentration and long residence time in liquid. A pressurized dissolution method based on decompression of liquid with dissolved gas is one of promising methods for generating fine micro-bubbles at high number density. Since the mechanism of micro-bubble generation is not clarified yet, design and improvement of micro-bubble generators are based on trial and error. In this study, effects of liquid volume flux at a decompression nozzle and dissolved gas concentration in the upstream region of the nozzle on diameter and number density of generated micro-bubbles are examined to understand generation mechanism of micro-bubbles in a pressurized dissolution method. The diameter and the number density of micro-bubbles are measured by using phase Doppler anemometry (PDA) in the downstream region of the nozzle, and the flow patterns in the nozzle are visualized by using a high-speed camera. The experimental results show that diameter and number density of generated micro-bubbles depend on cavitation pattern at the nozzle, and that cavitation bubbles containing not only vapor but also non-condensable gas become micro-bubbles due to their shrink caused by condensation of the vapor in the downstream region of the nozzle. (C) 2014 Elsevier Inc. All rights reserved.
ELSEVIER SCIENCE INC, 2015年01月, EXPERIMENTAL THERMAL AND FLUID SCIENCE, 60, 201 - 207, 英語[査読有り]
研究論文(学術雑誌)
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年, Multiphase Science and Technology, 27 (1), 67 - 75, 英語[査読有り]
研究論文(学術雑誌)
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, 2014年12月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 67, 111 - 121, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
Cavitation clouds shedding in a nozzle of fuel injector for Diesel Engines play a dominant role in the fuel spray atomization process and the subsequent spray combustion. Since a high speed cavitation flow in a tiny nozzle with a complicated geometry is not easy to be visualized and measured, large efforts have been paid to carry out numerical simulations of the transient cavitating flow in the nozzle. Most of the previous simulations are based on the Homogeneous Equilibrium Model (HEM), a simplified bubble dynamics model or a barotropic equation, and the Reynolds-Averaged Navier-Stokes (RANS) turbulence model, which do not predict the cavitation cloud shedding. Cavitation in the nozzle takes various forms, such as a transparent cavitation sheet and clouds of cavitation bubbles, which makes its prediction difficult. As a first step to develop a cavitation model which can accurately treat both the sheet and cloud cavitations, in this study we propose a new combination of Large Eddy Simulation (LES), Eulerian-Lagrangian Bubble Tracking Method (BTM), and the Rayleigh-Plesset (RP) equation to simulate an incipient cavitation, in which only cavitation bubble clouds appear. A precursor simulation of a fully developed turbulent flow in a channel, in which periodic boundary condition is adopted for the inlet and exit, is carried out to generate inlet boundary condition for a nozzle simulation. To verify the validity of the model, transient cavitation motion and turbulent velocity in a rectangular nozzle are acquired by using a high speed camera and Laser Doppler Velocimetry (LDV). As a result, a recirculation flow and a cavitation cloud shedding are accurately predicted by LES using a fine grid, and the RP equation for all nuclei tracked in a Lagrangian manner. (C) 2014 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2014年11月, COMPUTERS & FLUIDS, 103, 42 - 48, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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, 2014年06月01日, Journal of Computational Multiphase Flows, 6 (2), 111 - 126, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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, 2014年02月, JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY, 51 (2), 220 - 230, 英語[査読有り]
研究論文(学術雑誌)
Mass transfer from single carbon dioxide bubbles in vertical pipes is measured using a stereoscopic image processing method to develop a mass transfer correlation applicable to a wide range of bubble diameters in standard pipe sizes. The diameters of pipes used are 12.5, 18.2, and 25.0 mm and the bubble diameter ranges from 5 to 26 mm. The ratio, lambda, of the bubble diameter to the pipe diameter is varied from 0.2 to 1.8, which covers various bubble shapes such as spheroidal, wobbling, cap, and Taylor bubbles. Measured Sherwood numbers, Sh, strongly depend on bubble shape, i.e., Sh of Taylor bubbles differs from that of spheroidal and wobbling bubbles. The Sherwood numbers are correlated in terms of the Peclet number Pe and lambda. The applicability of the proposed correlation to long-term bubble dissolution process is examined through comparisons between measured and predicted dissolution processes. The predictions are carried out by solving mass conservation equations not only for carbon dioxide but also for nitrogen and oxygen. Good agreements are obtained in the dissolution processes for various bubble sizes and the three pipe diameters. (C) 2013 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2014年02月, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 69, 215 - 222, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
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.
PERGAMON-ELSEVIER SCIENCE LTD, 2014年01月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 58, 236 - 245, 英語[査読有り]
研究論文(学術雑誌)
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, 2014年01月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 58, 154 - 167, 英語[査読有り]
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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年, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 47 (3), 230 - 240, 英語[査読有り]
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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, 2013年12月, CHEMICAL ENGINEERING SCIENCE, 104, 166 - 176, 英語[査読有り]
研究論文(学術雑誌)
Optical measurement is an effective and accurate method to understand flow structures of multiphase flows. However, we frequently encounter difficulty in optical access due to the presence of interface and the complex geometry of a flow field. In the present study, we have developed small LDV optics to avoid the difficulty in optical access by installing the LDV probe into a channel component or by submerging the LDV probe into a flow field. The developed LDV optics consists of a manipulator and the probe. The manipulator splits a beam emitted from an Ar-ion laser into four beams. Each beam is introduced into an optical fiber through beam adjustment optics, and is transmitted to the probe through the fiber. The diameter of the probe is 7 mm. The laser beams emitted from the fibers in the probe are focused by a front lens of the probe and form a measurement volume. Scattered light from tracer particles are received by the probe and collected into a receiving fiber installed in the probe. The developed system is applied to laminar and turbulent flows in a rectangular duct for validation. Comparisons with a conventional LDV system show that the accuracy and reliability of the developed system are the same level as the conventional system. The application of the developed system to single-phase and bubbly flows in a 4 x 4 rod bundle demonstrates that the system has a large potential of measuring single-phase and multiphase flows in a channel with a complex geometry. (c) 2013 Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE SA, 2013年10月, NUCLEAR ENGINEERING AND DESIGN, 263, 342 - 349, 英語[査読有り]
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A multiscale approach for simulations of high Schmidt number mass transfer from bubbles into liquids is validated by detailed comparisons with experimental results. The approach is based on an embedded analytical description of the mass boundary layer next to the bubbles surface, coupled with a finite volume method for the rest of the domain. Two classes of bubbles are examined: Taylor bubbles in a pipe and freely rising bubbles. For the first class an axisymmetric domain is used, while for the latter a fully three-dimensional domain is used to capture the unsteady manner of a rising bubble. We also perform calculations of non-deformable freely rising bubbles for which we compare the computational results with analytical and semi-empirical correlations as well as experimental results from other authors. Mass transfer computations using the embedded analytical description approach show good agreement with the experimental results and the correlations. Based on the ratio of the thickness of the mass boundary layer to the grid size used to resolve the fluid flow we estimate that the use of the presented approach reduces the computational cost at least by one or two orders of magnitude, specially when applied in simulations of fully three-dimensional flows. © 2013 Elsevier Ltd.
Elsevier Ltd, 2013年09月20日, Chemical Engineering Science, 101, 165 - 174, 英語[査読有り]
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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.
2013年09月, Experimental Thermal and Fluid Science, 49, 160 - 168, 英語[査読有り]
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Turbulence intensities and Reynolds stresses of bubble-induced pseudo turbulence in air-water laminar bubbly flows in a vertical pipe of 20 mm diameter are measured at a low liquid Reynolds number, Re = 900. A pipe made of fluorinated ethylene propylene resin, which has the same refractive index as water, is utilized to enable the LDV measurement of Reynolds stresses. Experimental data show that (1) turbulence kinetic energy of bubble-induced turbulence is proportional to local void fraction, (2) the ratio among axial, radial and azimuthal components of turbulence intensity is 2:1:1, (3) Sato's eddy viscosity model underestimates the Reynolds shear stress of bubble-induced pseudo turbulence, whereas it qualitatively well represents the Reynolds stress distribution, (4) the Reynolds shear stress of bubble-induced turbulence depend not only on velocity gradient but also on gradient of void fraction and (5) the dissipation process of bubble-induced turbulence is analogous to that of shear-induced turbulence. (C) 2013 Elsevier Inc. All rights reserved.
ELSEVIER SCIENCE INC, 2013年04月, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, 40, 97 - 105, 英語[査読有り]
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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, 2013年03月01日, Journal of Computational Multiphase Flows, 5 (1), 27 - 41, 英語[査読有り]
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In most of the bubble column designs, it is assumed that the liquid phase is well mixed and spatial distributions of molar concentrations of all components are uniform. However, liquid mixing occurs in actual bubble columns. The performance of a bubble column strongly depends on the liquid mixing induced by bubbles in the column. The above-mensioned assumptions therefore lead to errors in the optimum column design. However, only a few quantitative investigations have been carried out on two-phase turbulence and liquid mixing. In this study, numerical simulations of liquid mixing in a bubble column were carried out and the results obtained were compared with those of experiments. Time-dependent tracer concentrations were measured for test columns 0.3 m in diameter. The height of the columns was 1 m. Bubbles were supplied by using two types of spargers, ring spargers and a perforated plate. A hybrid method, NP2-3D, that is based on a combination of multi-fluid and interface tracking models was used to simulate the flow. In a two-phase turbulence model, the linear superposition of bubble-induced turbulence and shear-induced turbulence was assumed. Numerical were found to be good predictions of the effects of the column diameter and gas inlet on the liquid mixing in the column.
SOC CHEMICAL ENG JAPAN, 2012年, JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 45 (9), 632 - 638, 英語[査読有り]
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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, 2011年04月, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, 37 (3), 241 - 251, 英語[査読有り]
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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.
2010年03月01日, Journal of Computational Multiphase Flows, 2 (1), 47 - 57, 英語[査読有り]
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3-D movement of flame fronts in lean and rich hydrocarbon-air turbulent premixed Bunsen flames, having the identical laminar burning velocities, were examined by a four-element electrostatic probe. Measurements were conducted at an off-axis position in turbulent flame brush. The probability distributions of the magnitude and of the direction cosines of the velocity vector of the flamelet were examined. The results showed differences between the lean and rich propane flames but not between the lean and rich methane-flame pairs. The lean propane flame has the same probability distribution of direction cosines as the methane flames. The probability distributions of the direction cosines for the rich propane flame are, however, quite different, that there is a much greater tendency for outward flamelet motion. Although these results for rich propane flame exhibit a larger most probable outward-motion direction cosine for burnt-to-unburnt passage than for unburnt-to-burnt passage, as has been found in all Bunsen-flame data and explained previously, this is the first example in Bunsen-flame data in which the most probable value of the direction cosine in the radial direction for unburnt to burnt passage is positive, that is, contrary to the other Bunsen-flame results, the average flamelet velocity direction is outward at this off axis position even for unburnt-to-burnt passage. The exceptional characteristics of rich propane were explained by nonlinear enhancement of the average flamelet burning velocity through preferential oxygen diffusion to turbulence-induced flamelet bulges convex towards the fresh mixture.
一般社団法人日本機械学会, 2008年08月, 日本機械学会論文集, Vol. 74, No. 744, Ser. B, pp. (744), 1835 - 1842, 日本語[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
Effects of inlet bubble diameter on void and bubble size distributions in poly-dispersed bubbly flow in a rectangular bubble column under high gas volumetric flux conditions are experimentally investigated. Three types of gas distributors are used to form bubbly flows with different inlet bubble diameters at a constant gas flow rate. The conclusions obtained are as follows : (1) the bubble size distribution reaches an equilibrium state at which the birth rate of bubbles belonging to a bubble group due to bubble breakup and coalescence is equal to the death rate at high gas volumetric flux, (2) distributions of void fraction and bubble diameter are not affected by inlet bubble diameters except for the region close to the air diffuser, and (3) the elevation at which the bubble size distribution reaches the equilibrium state becomes lower as the gas volumetric flux increases.
一般社団法人日本機械学会, 2008年06月, 日本機械学会論文集, Vol.74, No. 742, Ser. B, pp. 1 (742), 1368 - 1375, 日本語[査読有り]
研究論文(学術雑誌)
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研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
[招待有り]
研究論文(国際会議プロシーディングス)
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研究論文(国際会議プロシーディングス)
Cavitation in two-dimensional (2D) nozzles and liquid jet in the vicinity of the nozzle exit were visualized using high-speed cameras to investigate the effects of cavitation on liquid jet under various conditions of cavitation and Reynolds numbers sigma and Re. Liquid velocity in the nozzle was measured using a laser Doppler velocimetry to examine the effects of cavitation on the flow in the nozzle and liquid jet. As a result, the following conclusions were obtained: (1) cavitation in the nozzles and liquid jet can be classified into the four regimes: (no cavitation, wavy jet), (developing cavitation, wavy jet), (super cavitation, spray) and (hydraulic flip, flipping jet), (2) liquid jet near the nozzle exit depends on cavitation regime, (3) cavitation and liquid jet are not strongly affected by Re but by a, and (4) strong turbulence induced by the collapse of cavitation clouds near the exit plays an important role in ligament formation. (c) 2007 Elsevier Ltd. All rights reserved.
PERGAMON-ELSEVIER SCIENCE LTD, 2007年08月, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 50 (17-18), 3575 - 3582, 英語[査読有り]
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研究論文(学術雑誌)
[査読有り][招待有り]
研究論文(国際会議プロシーディングス)
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研究論文(学術雑誌)
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Numerical methods for predicting heterogeneous bubbly flows in bubble columns are indispensable in the design of bubble column reactors. The objectives of the present study are (1) to experimentally investigate the effects of a bubble size distribution on heterogeneous bubbly flows in an open vessel and (2) to examine the applicability of the NP2 model ((N+2)-field model) to heterogeneous bubbly flows. Distributions of void fraction and liquid velocity in air-water bubble plumes in the vessel were measured using an experimental setup with a bubble injection device by which the ratio of the volume flow rate of large bubbles to that of small bubbles was controlled to a desired value. The main conclusions obtained were as follows: (1) experimental data on the effects of bubble size distribution on air-water bubble plume were obtained, and (2) the NP2 model gave good predictions for heterogeneous bubbly plumes.
一般社団法人日本機械学会, 2006年11月, 日本機械学会論文集, Vol. 72, No. 723, (B), pp. 268 (723), 2680 - 2686, 日本語[査読有り]
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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 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.
一般社団法人日本機械学会, 2006年10月, 日本機械学会論文集, Vol. 72, No. 722, (B), pp. 241 (722), 2410 - 2417, 日本語[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In order to obtain the knowledge on the mechanism how cavitating flow in a nozzle enhances the liquid jet atomization, liquid velocity distributions of cavitating flows in a two dimensional transparent nozzle were measured using a Laser Doppler Velocimetry (LDV) system. As a result, the following conclusions were obtained: (1) The inception of cavitation occurs near the outer edge of the separated boundary layer (SBL), where the mean local velocity takes the highest value and the mean pressure is lower than the vapor saturation pressure. (2) When the cavitation number σ≥0.78 (No Cavitation or Developing Cavitation), the reattachment of SBL occurs in the middle of the nozzle. A large velocity fluctuation, which appears in and just downstream of SBL, decreases near the nozzle exit. This may be the reason of the wavy jet. (3) When σ≥0.65 (Super Cavitation), the lateral flow from the core region toward the side walls just upstream of the nozzle exit may be the major cause of the increase in spray angle and a drastic promotion of liquid jet atomization. The strong turbulence just upstream of the exit may also play a role on the formation of ligaments at liquid jet interface.
一般社団法人日本機械学会, 2006年02月, 日本機械学会論文集(B編), Vol. 72, No. 714, pp. 521-527 (714), 521 - 527, 日本語[査読有り]
研究論文(学術雑誌)
Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In the present study cavitation in a two-dimensional (2D) nozzle and the injected water jet were visualized using an ultra high-speed camera. As a result, the following conclusions were obtained: (1) The behavior of cavitation in the 2D nozzle and liquid jet agreed qualitatively with the previous observations of cylindrical nozzles. (2) When the cavitation number σ was 1.18, the inception of small cavitation bubbles was observed near the nozzle inlet apart from the side wall. (3) The number of cavitation bubble clouds increased with decreasing of σ (0.75≥σ<1.18), and the streamwise length of the cavitation region increased toward the middle of the nozzle (developing cavitation). The bubble clouds were clearly observed to recirculate in the separated boundary layer. In the case a wavy jet was observed with no significant effects of cavitation on liquid jet atomization. (4) With a slight decrease of σ from 0.75, the cavitation region suddenly extended to the nozzle exit (super cavitation). The shape of the cavitation region near the inlet became smooth, which imply the formation of a long cavitation bubble near the inlet. At the downstream half of the nozzle, clouds of cavitation appeared and collapsed intermittently within the nozzle. In the case atomization was promoted to form spray with ligaments and droplets.
一般社団法人日本機械学会, 2006年02月, 日本機械学会論文集(B編), Vol. 72, No. 714, pp. 513-520. (714), 513 - 520, 日本語[査読有り]
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An (N+2)-field model proposed in our previous study (Shimada and Tomiyama, 2005) was modified for application to compressible bubbly flows with chemisorption by taking into account the dependence of phase densities on components. Then, a numerical method for solving the modified (N+2)-field model was developed. The proposed method was verified through a sample calculation, i.e., a simulation of a bubbly flow with chemisorption in a rectangular vessel. Predictictions were compared with experiments. As a result, it was confirmed that the proposed method gave good predictions for the time evolutions of pH and gas holdup and for natural convection induced by the heat of reaction. Copyright © 2005 The Society of Chemical Engineers, Japan.
2005年, 化学工学論文集, 31 (6), 377 - 387, 日本語[査読有り]
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[査読有り]
その他
[査読有り]
その他
[査読有り]
その他
[査読有り]
その他
[査読有り]
その他
[査読有り]
その他
[査読有り]
その他
学術書
学術書
学術書
学術書
口頭発表(一般)
ポスター発表
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
シンポジウム・ワークショップパネル(指名)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
[招待有り]
シンポジウム・ワークショップパネル(指名)
シンポジウム・ワークショップパネル(指名)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(基調)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
[招待有り]
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
[招待有り]
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(招待・特別)
口頭発表(一般)
[招待有り]
口頭発表(招待・特別)
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
[招待有り]
口頭発表(招待・特別)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
ポスター発表
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
口頭発表(一般)
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金