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Idomura, Yasuhiro
Physics of Plasmas, 24(8), p.080701_1 - 080701_5, 2017/08
Times Cited Count：10 Percentile：45.63(Physics, Fluids & Plasmas)An electron heating modulation numerical experiment based on a global full-f gyrokinetic model shows that transitions from ion temperature gradient driven (ITG) turbulence to trapped electron mode (TEM) turbulence induced by electron heating generate density peaking and rotation changes. Toroidal angular momentum balance during the rotation changes is revealed by direct observation of toroidal angular momentum conservation, in which in addition to ion turbulent stress, ion neoclassical stress, radial currents, and toroidal field stress of ions and electrons are important. Toroidal torque flipping between ITG and TEM phases is found to be related to reversal of the ion radial current that indicates coupling of particle and momentum transport channels. The ion and electron radial currents are balanced to satisfy the ambipolar condition, and the electron radial current is cancelled by the electron toroidal field stress, which indirectly affects toroidal torque.
Kishimoto, Yasuaki
Purazuma, Kaku Yugo Gakkai-Shi, 80(5), p.390 - 395, 2004/05
High performance magnetically confined plasma is realized by having structures in plasmas, where different elementary processes with different time and spatial scales are deeply contributing with each other. A research based on large scale simulation is then essential to understand such hierarchical complex plasmas. We discuss the underlying physical process of the structural plasma and present a prospect for future numerical simulations covering a wide dynamical range.
Ida, Masato; Taniguchi, Nobuyuki*
Physical Review E, 69(4), p.046701_1 - 046701_9, 2004/04
Times Cited Count：1 Percentile：5.79(Physics, Fluids & Plasmas)This paper extends our recent theoretical work concerning the feasibility of stable and accurate computation of turbulence using a large eddy simulation. In our previous paper, it was shown, based on a simple assumption regarding the instantaneous streamwise velocity, that the application of the Gaussian filter to the Navier-Stokes equations can result in the appearance of a numerically unstable term. In the present paper, based on assumptions regarding the statistically averaged velocity, we show that in several situations, the shears appearing in the statistically averaged velocity field numerically destabilize the fluctuation components because of the derivation of a numerically unstable term that represents negative diffusion in a fixed direction. This finding can explain the problematic numerical instability that has been encountered in large eddy simulations of wall-bounded flows. The present result suggests that if there is no failure in modeling, the resulting subgrid-scale model can still have unstable characteristics.
Bruskin, L. G.; Oyama, Naoyuki; Shinohara, Koji; Miura, Yukitoshi; Kogi, Yuichiro*; Mase, Atsushi*; Hasegawa, Makoto*; Hanada, Kazuaki*
Review of Scientific Instruments, 74(3), p.1473 - 1476, 2003/03
Times Cited Count：5 Percentile：33.12(Instruments & Instrumentation)An analytical model of fluctuation reflectometry is developed, which is capable of handling the plasma profiles of arbitrary shape and curvature. The experimental profiles are piece-wise approximated by the functions, which allow for the integration of the full-wave O-mode equation. The model is applied to the reflectometry of the JT-60U tokamak plasma to provide a preliminary estimation of the fluctuation amplitude and spectral width.
Li, J.; Kishimoto, Yasuaki
Physics of Plasmas, 9(4), p.1241 - 1254, 2002/04
Times Cited Count：37 Percentile：72.43(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.
Kataoka, Isao*; Matsuura, Keizo*; Yoshida, Kenji*
JAERI-Tech 2002-015, 83 Pages, 2002/03
JAERI-Tech-2002-015.pdf:3.62MB
no abstracts in English
Kunugi, Tomoaki; *; *
Nihon Kikai Gakkai Rombunshu, B, 60(573), p.1751 - 1757, 1994/05
no abstracts in English
*; *; *; Kunugi, Tomoaki
Therm. Sci. Eng., 2(2), p.16 - 25, 1994/00
no abstracts in English
Yokokawa, Mitsuo;
Joho Shori Gakkai Kenkyu Hokoku, 93(33), p.37 - 44, 1993/04
no abstracts in English
Yamazawa, Hiromi
JAERI-M 90-128, 36 Pages, 1990/08
no abstracts in English
Yamazawa, Hiromi
JAERI-M 89-082, 43 Pages, 1989/06
no abstracts in English
Kawai, Chika; Idomura, Yasuhiro; Maeyama, Shinya; Ogawa, Yuichi*
no journal, ,
In estimating confinement properties of fusion plasmas, it is a critical issue to understand structures of turbulent spectra, leading to turbulent transport. In this study, self-organization processes, which produce zonal flows from electron turbulence, are analyzed in detail via a highly accurate gyrokinetic Eulerian code, and structures of turbulent spectra leading to zonal flow generation are clarified.
Idomura, Yasuhiro
no journal, ,
Numerical experiments of hydrogen (H) and deuterium (D) plasmas with ion and electron heating conditions were conducted using the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D. The energy confinement time in the ion heated numerical experiments was almost independent of isotope mass, and the plasma size scaling gives Bohm scaling. On the other hand, the electron heated numerical experiments showed a clear isotope effect. In this case, in addition to the plasma size scaling, the isotope dependency of the collisional energy transfer from electrons to ions contributed to the total isotope scaling by enhancing the ion heat transport channel. Systematic electron heating power scans for the H and D plasmas showed similar ion and electron temperature profiles at an H to D heating power ratio of 1.4. These results qualitatively agree with the isotope scaling in L-mode experiments with ion and electron heating conditions.
