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Journal Articles

Development of a multiphase particle method for melt-jet breakup behavior of molten core in severe accident

Wang, Z.; Iwasawa, Yuzuru; Sugiyama, Tomoyuki

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 12 Pages, 2020/08

Journal Articles

Large-scale direct simulation of two-phase flow structure around a spacer in a tight-lattice nuclear fuel bundle

Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Akimoto, Hajime

Computational Fluid Dynamics 2004, p.649 - 654, 2006/00

no abstracts in English

Journal Articles

Numerical analysis of a water-vapor two-phase film flow in a narrow coolant channel with a three-dimensional rectangular rib

Takase, Kazuyuki; Yoshida, Hiroyuki; Ose, Yasuo*; Tamai, Hidesada

JSME International Journal, Series B, 47(2), p.323 - 331, 2004/05

no abstracts in English

Journal Articles

Numerical study of zonal flow dynamics and electron transport in electron temperature gradient driven turbulence

Li, J.; Kishimoto, Yasuaki

Physics of Plasmas, 11(4), p.1493 - 1510, 2004/04

 Times Cited Count:57 Percentile:87.05(Physics, Fluids & Plasmas)

The electron temperature gradient (ETG) driven turbulence in tokamak core plasmas is numerically investigated based on three-dimensional gyrofluid model with adiabatic ion response. Attentions are focused on the zonal flow dynamics in ETG fluctuations and the resultant electron heat transport. A high electron energy confinement mode is found in the weak magnetic shear regime, which is closely relevant with self-organization behavior of turbulence through the enhanced zonal flow dynamics rather than the weak shear stabilization of ETG fluctuations. It is demonstrated that the weak shear is favorable for the enhancement of zonal flows in ETG turbulence.

Journal Articles

Saturation of zonal flow in gyrofluid simulations of electron temperature gradient driven turbulence

Li, J.; Kishimoto, Yasuaki; Idomura, Yasuhiro; Miyato, Naoaki; Matsumoto, Taro

Journal of Plasma and Fusion Research SERIES, Vol.6, p.585 - 588, 2004/00

An enhanced zonal flow is observed in collisionless electron temperature gradient (ETG) driven turbulence with weak magnetic shears. The Kelvin-Helmholtz (KH) instability is proposed as a primary damping mechanism of such flow. Some considerable evidences for the KH mode excitation are presented. Results seem to suggest a possibility of turbulence transition from the ETG-dominated one to the KH-dominated one due to the zonal flow dynamics in weak shear plasmas.

Journal Articles

Experimental study on thermal-hydraulics and neutronics coupling effect on flow instability in a heated channel with THYNC facility

Iguchi, Tadashi; Shibamoto, Yasuteru; Asaka, Hideaki; Nakamura, Hideo

Proceedings of 10th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-10), 16 Pages, 2003/10

Thermal-hydraulic and neutronic dynamics are always interrelated in BWR core. This is called thermal-hydraulic and neutronic (T/N) coupling. Channel stability experiments with T/N coupling under non-nuclear condition are very limited. This is mainly due to the difficulties in the real-time simulation of neutron dynamics and in the fast-response void fraction measurement under high-pressure and temperature conditions. Authors have developed techniques to solve the above difficulties, and have succeeded in experimentally simulating T/N coupling under non-nuclear conditions with the THYNC facility. Using THYNC facility, T/N coupling effect on channel stability was investigated. Experiments were performed under Pressure=2-7MPa, Subcooling=10-40K, and Mass flux=270-660kg/m$$^{2}$$s. THYNC results indicated T/N coupling lowered the channel stability threshold. The reduction of channel stability threshold due to T/N coupling was small within 10% at 7MPa in the present THYNC experiment, although the experimental condition was set to be more severe than that supposed in a reactor.

Journal Articles

Experimental study on cooling limit under flow instability in boiling flow channel

Iguchi, Tadashi; Shibamoto, Yasuteru; Asaka, Hideaki; Nakamura, Hideo

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 8 Pages, 2003/04

Authors investigated the cooling limit under flow instability, by conducting THYNC experiments using a 2$$times$$2 bundle test section of electrical rod heaters、whose heated lengths and diameters were 3.71m and 12.3mm. The experimental result indicated periodic rise and rapid drop of the rod temperature under flow oscillation, indicating periodic film boiling. When the heating power increased further, the rod temperature indicated continuous film boiling. The power at the onset of continuous film boiling (cooling limit) under flow oscillation was about 50%-80% of the cooling limit under steady flow condition in THYNC. The ratio of both cooling limits almost agreed with the Umekawa model prediction in cases of P$$<$$2MPa and G$$<$$400kg/m2s. For high pressure and high mass flux conditions, the ratio almost agreed with the empirical model based on the heat balance during one cycle of flow oscillation. TRAC-BF1 code simulated periodic film boiling qualitatively, but the cooling limit under the flow oscillation was not predicted well probably due to inaccurate rewetting prediction.

Journal Articles

Interaction between small-scale zonal flows and large-scale turbulence; A Theory for ion transport intermittency in tokamak plasmas

Li, J.; Kishimoto, Yasuaki

Physical Review Letters, 89(11), p.115002_1 - 115002_4, 2002/09

 Times Cited Count:31 Percentile:78.24(Physics, Multidisciplinary)

Interaction between small-scale zonal flows and large-scale turbulence is investigated. The key mechanism is identified as radially non-local mode coupling. Fluctuating energy can be non-locally transferred from the unstable longer to stable or damped shorter wavelength region, so that turbulence spectrum is seriously deformed and deviated from the nonlinear power law structure. Three-dimensional gyro-fluid ion temperature gradient (ITG) turbulence simulations show that an ion transport bursting behavior is consistently linked to the spectral deformity with the causal role of ITG-generated zonal flows in tokamak plasmas.

Journal Articles

Zonal flows in gyrofluid simulations of slab electron temperature gradient turbulence

Li, J.; Kishimoto, Yasuaki

Physics of Plasmas, 9(4), p.1241 - 1254, 2002/04

 Times Cited Count:35 Percentile:73.62(Physics, Fluids & Plasmas)

Zonal flows can be generated by drift wave turbulence through the nonlinear interactions. 3-D gyrofluid simulations show that in a turbulent system driven by electrostatic sheared slab electron temperature gradient(ETG) modes, the excitation of zonal flows is a slower process that indicates the amplitudes grow up approximately proportionally to time. The zonal flows are very weak comparing with the background turbulence and hardly work for suppressing the turbulent electron heat transport. The dynamics of zonal flows is numerically explored through starting zonal flow component in the quasi-steady state.

Journal Articles

Investigation on natural circulation two-phase flow instability

J.U.Knebel*; Araya, Fumimasa

Proc. of 2nd Japanese-German Symp. on Multi-phase Flow, p.447 - 453, 1997/00

no abstracts in English

Journal Articles

Interfacial friction factor for high-pressure steam/water stratified-wavy flow in horizontal pipe

Nakamura, Hideo; Kukita, Yutaka; *

Journal of Nuclear Science and Technology, 32(9), p.868 - 879, 1995/09

 Times Cited Count:4 Percentile:37.69(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Analysis of density wave instability in a boiling flow using a characteristic method

Transient Thermal Hydraulics,Heat Transfer,Fluid-structue Interaction,and Structural Dynamics,ASME94, 0, p.65 - 73, 1994/00

no abstracts in English

JAEA Reports

Journal Articles

Flow regime transition in high-pressure large-diameter horizontal two-phase flow

Anoda, Yoshinari; Kukita, Yutaka; Nakamura, Hideo; Tasaka, Kanji

Proc. on 1989 National Heat Transfer Conf., Vol. 4, 8 Pages, 1989/00

no abstracts in English

Journal Articles

Extended semicircle and semi-ellipse theorems for the heterogeneous swirling flow of an incompressible fluid

Journal of the Physical Society of Japan, 54(5), p.1769 - 1781, 1985/00

 Times Cited Count:0 Percentile:0.01(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Semicircle theorem for the rotating flow in an azimuthal magnetic field with respect to azimuthal perturbations

Journal of the Physical Society of Japan, 53(5), p.1587 - 1589, 1984/00

 Times Cited Count:1 Percentile:40.76(Physics, Multidisciplinary)

no abstracts in English

17 (Records 1-17 displayed on this page)
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