Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Uesawa, Shinichiro; Ono, Ayako; Nagatake, Taku; Yamashita, Susumu; Yoshida, Hiroyuki
Journal of Nuclear Science and Technology, 62(5), p.432 - 456, 2025/05
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)We performed electrostatic simulations of a wire-mesh sensor (WMS) for a single spherical bubble and bubbly flow to clarify the accuracy of the WMS. The electrostatic simulation for the single bubble showed the electric current density distribution and the electric current path from the excited transmitter to receivers for various bubble locations. It indicated systematic errors based on the nonuniform current density distribution around the WMS. The electrostatic simulation for the bubbly flow calculated by the computational fluid dynamics code, JAEA Utility Program for Interdisciplinary Thermal-hydraulics Engineering and Research (JUPITER), indicated that the WMS had difficulty in quantitatively measuring the intermediate values of the instantaneous void fraction between 0 and 1 because they cannot be estimated by previous transformation methods from the WMS signal to the void fraction, such as linear approximation or Maxwell's equation, and have a significant deviation of the void fraction of 
0.2 for the WMS signal. However, the electrostatic simulation indicated that the time-averaged void fractions around the center of the flow channel can be estimated using linear approximation, and the time-averaged void fraction near the wall of the flow channel can be estimated using Maxwell's equation.
Uesawa, Shinichiro; Ono, Ayako; Yamashita, Susumu; Yoshida, Hiroyuki
Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 7 Pages, 2024/11
A conductance-typed wire-mesh sensor (WMS), utilizing the difference in conductivity between gas and liquid phases between the electrodes, is one of the practical measurement techniques of a cross-sectional void fraction distribution in a flow path. In this study, we performed two-phase computational fluid dynamics (CFD) and electrostatic simulations around a WMS for a single spherical bubble and bubbly flow to clarify the systematic error in the WMS. The results for the single bubble indicated that there were systematic errors based on the non-uniform current density distribution around the WMS. The correlation between instantaneous void fractions and WMS signals is not uniquely determined for positions of the single bubble moving across the WMS, even for the same bubble. Moreover, the correlation between the instantaneous void fractions and the WMS signals did not fit in a linear approximation and Maxwell's equation, which traditionally used transformation methods from the WMS signal to the void fraction. The results for the bubbly flow indicated that the WMS had difficulty in quantitative measurements of the instantaneous void fraction because the values had a significant deviation of the void fraction of approximately 0.2. On the other hand, time-averaged void fraction values had relatively small deviation. Thus, we concluded that the WMS, using existing transformation methods, can measure time-averaged void fractions, but it is difficult to measure quantitatively instantaneous void fractions.
Wada, Yuki; Hirose, Yoshiyasu; Shibamoto, Yasuteru
Ultrasonics, 141, p.107346_1 - 107346_16, 2024/07
Times Cited Count：2 Percentile：53.22(Acoustics)Ono, Ayako; Okamoto, Kaoru*; Makino, Yasushi*; Hosokawa, Shigeo*; Yoshida, Hiroyuki
Proceedings of Specialist Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal-Hydraulics and Severe Accidents (SWINTH-2024) (USB Flash Drive), 13 Pages, 2024/06
JAEA has been developing an advanced neutronic/thermal-hydraulics coupling simulation system. In the coupling simulation system, the detailed thermal-hydraulics codes based on an interface-capturing method (JUPITER or TPFIT) will be adopted to simulate thermal-hydraulics behavior in a fuel bundle. The experimental data and findings relating to the gas-liquid two-phase flow in a fuel bundle are especially required to validate JUPITER/TPFIT. In this study, we therefore develop a measurement method by combining Laser-Doppler Velocimetry (LDV) and photodiodes, which can access to a small flow channel such as a subchannel of a fuel bundle. The developed measurement method is validated by comparison with the measument by a electrical conductance probe. Finally, we obtain experimental data on local flow structures and interactions between gas and liquid phases. The developed measurement method is actually applied to an air-water dispersed bubbly flow to confirm its capability.
Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09
An experimental study on the upward bubbly air-water flows in a vertical large-diameter square duct have been performed by using four-sensor probes. The four-sensor probe were applied in the local measurements at 3 axial positions along the flow direction to obtain interfacial area concentration, 3-D bubble velocity vector and bubble diameter. The obtained void fraction, interfacial area concentration, 3-D bubble velocity vector and bubble diameter provided valuable insight into the flow structure and will serve as a valuable database to develop the mechanistic models for interfacial area transport equation sources and sinks.
Shen, X.*; Sun, Haomin; Deng, B.*; Hibiki, Takashi*; Nakamura, Hideo
Progress in Nuclear Energy, 89, p.140 - 158, 2016/05
Times Cited Count：25 Percentile：89.55(Nuclear Science & Technology)An experimental study was performed on the local structure of upward air-water two-phase flow in a vertical large diameter square duct by using a four-sensor probe. The four-sensor probe method classifying spherical and non-spherical bubbles was applied as a key measurement way to obtain local parameters such as 3-D bubble velocity vector, bubble diameter and interfacial area concentration. Both the local void fraction and interfacial area concentration indicated radial core-peak and wall-peak distributions at low and high liquid flow rates respectively. The 2 components of the bubble velocity vector in the cross-section revealed that there exists a rotating secondary flow in the octant symmetric triangular area and the magnitude of the rotating secondary flow increases with the liquid flow rate. Some of constitutive correlations of drift-flux model and interfacial area concentration are reviewed to study their predictabilities against the present data.
Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Akimoto, Hajime
Proceedings of 2005 ASME International Mechanical Engineering Congress and Exposition (CD-ROM), 8 Pages, 2005/11
no abstracts in English
Takase, Kazuyuki; Yoshida, Hiroyuki; Akimoto, Hajime; Ose, Yasuo*; Aoki, Takayuki*
Nihon Kikai Gakkai 2005-Nendo Nenji Taikai Koen Rombunshu, Vol.7, p.17 - 18, 2005/09
no abstracts in English
Takase, Kazuyuki; Yoshida, Hiroyuki; Tamai, Hidesada; Ose, Yasuo*
Nihon Kikai Gakkai 2004-Nendo Nenji Taikai Koen Rombunshu, Vol.2 (No.04-1), p.251 - 252, 2004/09
no abstracts in English
Onuki, Akira; Akimoto, Hajime
Journal of Nuclear Science and Technology, 38(12), p.1074 - 1080, 2001/12
Multi-dimensional analyses have been expected recently with expanding computation resources for gas-liquid two-phase flow analyses of advanced nuclear systems such as passive safety systems and natural-circulation-type reactors. However, the applicability of previous constitutive equations for multi-dimensional analyses has not been fully investigated especially for the effects of flow path scale because the equations have been assessed for small-scale experiments. In this study, we analyzed the scale effects by the multi-dimensional two-fluid model code using data in 38 mm and 200 mm diameter pipes. We clarified a key-parameter to model the scale effects and developed models for the effects on phase distribution. The scale effects can be classified by the relative relationship between bubble diameter db and turbulent length scale lT. Bubble-induced turbulence is increased under that db is smaller than lT and bubble coalescence is predominated rather than breakup under that lT is about three times larger than db and under higher void fraction. Based on these findings, we established new models for bubble turbulent diffusion and bubble diameter. The applicability was promising through assessments against the 38 mm and 200 mm pipes under different flow rates and against a database for developing flow along 480 mm pipe.
Onuki, Akira; Akimoto, Hajime
Proceedings of the 8th International Symposium on Flow Modeling and Turbulence Measurements (FMTM2001) (CD-ROM), 7 Pages, 2001/12
Multi-dimensional analyses have been expected with expanding computation resources for gas-liquid two-phase flow. We recently developed models for bubble turbulent diffusion and bubble diameter to predict the phase distribution by a multi-dimensional two-fluid model. This study was performed to verify our model. The verification was performed using databases under diameter; 9 mm to 155 mm, pressure; atmospheric to 4.9 MPa, flow rate; superficial gas velocity = 0.01 to 5.5 m/s and superficial liquid one = 0.0 to 4.3 m/s, fluid combination; air-water or steam-water. Through the assessments, our model was found to be applicable to the wide range of flow conditions including the effect of pipe diameter. The shape of phase distribution and the average void fraction are predicted well qualitatively and quantitatively. Since the model is established using the ratio of bubble diameter to eddy size as a key-parameter, the ratio is one of important parameters to develop the constitutive equations in the multi-dimensional two-fluid model.
Onuki, Akira; Akamatsu, Mikio*; Akimoto, Hajime
Nihon Konsoryu Gakkai Dai-5-Kai Oganaizudo Konsoryu Foramu Hobunshu, p.87 - 92, 2001/09
Multi-dimensional analyses have been expected with expanding computation resources for gas-liquid two-phase flow in a complex geometry such as fuel rod bundles. Japan Atomic Energy Research Institute is developing a numerical analytical method for the geometry effect, which is based on three-dimensional two-fluid model. In this study, a general curvilinear coordinate system was introduced to the two-fluid model code ACE-3D and air-water two-phase flow around a circular cylinder was analyzed. The present method predicts an air concentration to vortex regions behind the cylinder and a temporal fluctuation of vortex intensity; these two phenomena have been observed in experiments. It is clarified that the phenomena depend on a relative relationship between the drag force and the inertia of bubbles due to pressure fields.
Watanabe, Tadashi; Ebihara, Kenichi
Proceedings of 4th International Conference on Supercomputing in Nuclear Applications (SNA 2000) (CD-ROM), 10 Pages, 2000/09
no abstracts in English
Onuki, Akira; Akimoto, Hajime
International Journal of Multiphase Flow, 26(3), p.367 - 386, 2000/03
Times Cited Count：139 Percentile：96.04(Mechanics)no abstracts in English
Onuki, Akira; ; Akimoto, Hajime
Konsoryu Shimpojiumu '98 Koen Rombunshu, p.221 - 222, 1998/00
no abstracts in English
Onuki, Akira; Akimoto, Hajime
Proc. of 3rd Int. Conf. on Multiphase Flow (ICMF'98), p.1 - 6, 1998/00
no abstracts in English
Onuki, Akira; Kamo, Hideki*; Akimoto, Hajime
Eighth Int. Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-8), 3, p.1670 - 1676, 1997/00
no abstracts in English
Onuki, Akira; Kamo, Hideki*;
Proceedings of Japan-US Seminar on Two-Phase Flow Dynamics, 0, p.75 - 82, 1996/00
no abstracts in English
Onuki, Akira;
Proc. of ASME Heat Transfer and Fluids Engineering Divisions (HTD-Vol. 321,FED-Vol. 233), 0, p.473 - 478, 1995/00
no abstracts in English
Onuki, Akira; ; Sudo, Yukio
Proc. of the 2nd Int. Conf. on Multiphase Flow 95-Kyoto, 0, p.FT1.17 - FT1.23, 1995/00
no abstracts in English
