Shearing rate of time-dependent E x B flow
Shearing rate of time-dependent E x B flow
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DOI：
10.1063/1.873331
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发表时间：
1999-03-01
影响因子：
2.2
通讯作者：
Tang, WM
中科院分区：
文献类型：
--
作者：
Hahm, TS;Beer, MA;Tang, WM
环形几何中湍流的 ExB 剪切抑制理论 [Phys。 Plasmas 2, 1648 (1995)] 被扩展为包括在托卡马克湍流非线性模拟中经常观察到的 ExB 流的快速时间变化。结果表明，ExB 流的快速时变分量虽然通常对瞬时 ExB 剪切速率有显着贡献，但在抑制湍流方面不如缓慢时变分量有效。这是因为在涡流充分扭曲之前剪切流模式发生了变化。捕捉这一重要物理现象的有效 ExB 剪切速率是根据陀螺流体模拟的区域流统计分析推导和估计的。这为理解最近的回旋流体和回旋运动模拟提供了新的见解，这些模拟在存在湍流驱动的层流的情况下产生降低但未完全淬灭的湍流水平。 (C) 1999 年美国物理研究所。 [S1070-664X(99)04603-0]。
Theory of ExB shear suppression of turbulence in toroidal geometry [Phys. Plasmas 2, 1648 (1995)] is extended to include fast time variations of the ExB flows often observed in nonlinear simulations of tokamak turbulence. It is shown that the quickly time varying components of the ExB flows, while they typically contribute significantly to the instantaneous ExB shearing rate, are less effective than the slowly time varying components in suppressing turbulence. This is because the shear flow pattern changes before eddies get distorted enough. The effective ExB shearing rate capturing this important physics is analytically derived and estimated from zonal flow statistics of gyrofluid simulation. This provides new insights into understanding recent gyrofluid and gyrokinetic simulations that yield a reduced, but not completely quenched, level of turbulence in the presence of turbulence-driven zonal flows. (C) 1999 American Institute of Physics. [S1070-664X(99)04603-0].