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Shen, X.*; Schlegel, J. P.*; Hibiki, Takashi*; Nakamura, Hideo
Nuclear Engineering and Design, 333, p.87 - 98, 2018/07
Times Cited Count：11 Percentile：32.69(Nuclear Science & Technology)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; Nakamura, Hideo; Kawamura, Shinichi*; Saishu, Sadanori*
Nihon Kikai Gakkai Netsu Kogaku Koenkai Koen Rombunshu, p.31 - 32, 2001/11
A passive containment cooling system (PCCS) is under planning to use in a next-generation-type BWR for long-term cooling by condensing steam using horizontal heat exchangers. Heat transfer behavior in a secondary water pool is one of important phenomena governing heat removal performance of the PCCS. Boiling and condensation can be supposed under high heat flux regions and the characteristics of the two-phase natural circulation should be evaluated. This study investigated effects of pool size on the characteristics by multi-dimensional two-fluid model code ACE-3D. It was found from the analyses that the pool size gives no significant influences for the characteristics in tube bundle under local-boiling mode.
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.
Onuki, Akira; Nakamura, Hideo; Anoda, Yoshinari; Obata, Hiroyuki*; Saishu, Sadanori*
Proceedings of 9th International Conference on Nuclear Engineering (ICONE-9) (CD-ROM), 10 Pages, 2001/00
A passive containment cooling system (PCCS) is under planning to use in a next-generation-type BWR for long-term cooling by condensing steam using horizontal heat exchangers. Heat transfer behavior in a secondary water pool is one of important phenomena governing heat removal performance of the PCCS. Boiling and condensation can be supposed under high heat flux regions and the two-phase natural circulation might enhance the heat transfer due to an increase of flow rate and a flow agitation. However, some heat transfer tubes might be covered only by steam and the heat transfer is degraded in such region (Steam-blanket effect). This study evaluated the characteristics of the heat transfer behavior in the secondary water pool by multi-dimensional two-fluid model code ACE-3D. It was found from the analyses that no any heat transfer tubes are covered only by steam and the heat transfer is enhanced due to the nucleate boiling and the increase of local liquid flow rate.
Onuki, Akira; Akimoto, Hajime
Proceedings of 2nd Japanese-European Two-Phase Flow Group Meeting (CD-ROM), 6 Pages, 2000/00
no abstracts in English
Onuki, Akira; Kamo, Hideki*; Akimoto, Hajime
JAERI-Data/Code 99-038, 108 Pages, 1999/08
JAERI-Data-Code-99-038.pdf:5.2MB
no abstracts in English
Onuki, Akira; Akimoto, Hajime
Proc. of 1st European-Japanese Two-phase Flow Group Meeting, p.1 - 8, 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;
Proc. of 5th Int. Topical Meeting on Nuclear Thermal Hydraulics,Operations and Safety, 00(00), p.1 - 6, 1997/04
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*;
JAERI-Data/Code 96-033, 76 Pages, 1996/11
JAERI-Data-Code-96-033.pdf:1.92MB
no abstracts in English
Onuki, Akira; Araya, Fumimasa;
PHOENICS J. Comput. Fluid Dyn. Its Appl., 9(3), p.326 - 342, 1996/09
no abstracts in English
; Murao, Yoshio
Journal of Nuclear Science and Technology, 33(4), p.290 - 297, 1996/04
Times Cited Count：3 Percentile：32.72(Nuclear Science & Technology)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
G.R.Noghrehkar*; Kawaji, Masahiro*; A.M.C.Chan*; Nakamura, Hideo; Kukita, Yutaka
J. Fluids Eng., 117, p.1 - 9, 1995/03
no abstracts in English
; Abe, Yutaka*; Onuki, Akira; Murao, Yoshio
JAERI-Data/Code 94-006, 40 Pages, 1994/07
JAERI-Data-Code-94-006.pdf:1.26MB
no abstracts in English
Abe, Yutaka; ; Kamo, Hideki*; Murao, Yoshio
Journal of Nuclear Science and Technology, 30(12), p.1214 - 1224, 1993/12
Times Cited Count：3 Percentile：38.1(Nuclear Science & Technology)no abstracts in English
; Onuki, Akira; Murao, Yoshio
JAERI-M 93-027, 66 Pages, 1993/02
no abstracts in English
