JOPSS - Search Results

Journal Articles

Zonal flow and GAM dynamics and associated transport characteristics in reversed shear tokamaks

Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.*

Journal of Plasma Physics, 72(6), p.821 - 824, 2006/12

https://doi.org/10.1017/S0022377806004946

Times Cited Count：0 Percentile：0.01(Physics, Fluids & Plasmas)

Zonal flow behaviour and its effect on turbulent transport in reversed shear tokamaks are investigated by global nonlinear simulation of ion temperature gradient driven turbulence. When safety factor is reduced, zonal flows in a minimum region change from oscillatory ones to stationary ones and suppress the turbulent transport effectively. This result indicates that the change of zonal flow behaviour in the minimum region may trigger the formation of ion transport barriers.

Journal Articles

Global profile effects and structure formations in toroidal electron temperature gradient driven turbulence

Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki

Nuclear Fusion, 45(12), p.1571 - 1581, 2005/12

https://doi.org/10.1088/0029-5515/45/12/012

Times Cited Count：39 Percentile：74.86(Physics, Fluids & Plasmas)

Using a global gyrokinetic toroidal particle code, the toroidal electron temperature gradient driven (ETG) turbulence is studied in positive and reversed shear tokamaks. In the nolinear turbulent state, the ETG turbulence in the positive and reversed shear configurations show quite different structure formations. In the positive shear configuration, the ETG turbulence is dominated by streamers which have a ballooning type structure, and the electron temperature profile is quickly relaxed to the marginally stable state in a turbulent time scale. In the reversed shear configuration, quasi-steady zonal flows are produced in the regative shear region, while the positive shear region is characterized by streamers. Accordingly, the electron thermal diffusivity has a gap structure across the $q_{min}$ surface, and the gradinet is sustained above the marginal value for a long time in the quasi-steady phase. The results suggest a stiffness of the profile in positive shear tokamaks, and a possibility of the Te transport barrier in reversed shear tokamaks.

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

https://doi.org/10.1063/1.1669397

Times Cited Count：59 Percentile：85.15(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

Geometrical improvements of rotational stabilization of high- ballooning modes in tokamaks

Furukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*

Nuclear Fusion, 43(6), p.425 - 429, 2003/06

https://doi.org/10.1088/0029-5515/43/6/305

We have found numerically that damping phases appear in the time evolution of the perturbation energy of high- ballooning modes in the presence of toroidal shear flows. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of X-point at inner side of the torus enhance the stabilization effect of the toroidal flow through this mechanism.

Journal Articles

Geometrical improvements of rotational stabilization of high- ballooning modes in tokamaks

Furukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*

Nuclear Fusion, 43(6), p.425 - 429, 2003/06

https://doi.org/10.1088/0029-5515/43/6/305

Times Cited Count：10 Percentile：31.59(Physics, Fluids & Plasmas)

We have found numerically that damping phases appear in the time evolution of the perturbation energy of high- ballooning modes in the presence of toriodal flow shear, where n is a toroidal mode number. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of an X-point at inner side of the torus enhance the stabilization effect of the toroidal flow shear through this mechanism.

Journal Articles