Suppression of turbulence and transport by sheared flow
Suppression of turbulence and transport by sheared flow
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DOI：
10.1103/revmodphys.72.109
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发表时间：
2000
影响因子：
44.1
通讯作者：
P. Terry
中科院分区：
文献类型：
--
作者：
P. Terry
回顾了稳定剪切流在抑制等离子体和中性流体中的湍流和湍流传输中的作用。局部稳定流剪切产生传输障碍，其在聚变装置中的广泛和高度成功的应用使其成为减少甚至消除聚变级等离子体特征的热量和粒子快速湍流损失的主要实验技术。这些传输势垒发生在具有不同物理特性和一系列限制配置的不同等离子体区域，表明物理过程具有不同寻常的普遍性。流动剪切通过加速湍流去相关来抑制湍流。每当稳定平均流剪切的应变率超过非线性去相关率时，这就是平流的一个鲁棒特征。剪切应变降低了剪切方向上的相关长度并降低了湍流振幅。它还扰乱了湍流的其他过程，包括重要集体模式的线性不稳定性、平流流体和平流物之间产生运输的相关性，以及大规模空间连接的雪崩式运输事件。在等离子体中，稳定流剪切区域可以由外部驱动，但最常见的是在不同等离子体状态之间的关键转变中自发产生。剪切抑制发生在流体动力学中，代表了快速畸变理论对二维稳定剪切流中长时间尺度非线性状态的扩展。流体动力学的例子包括衰减的二维纳维-斯托克斯湍流中相干涡流的出现以及平流层中湍流传输的减少。 (c) 2000 年美国物理学会。 “ 较少的
The role of stable shear flow in suppressing turbulence and turbulent transport in plasmas and neutral fluids is reviewed. Localized stable flow shear produces transport barriers whose extensive and highly successful utilization in fusion devices has made them the primary experimental technique for reducing and even eliminating the rapid turbulent losses of heat and particles that characterize fusion-grade plasmas. These transport barriers occur in different plasma regions with disparate physical properties and in a range of confining configurations, indicating a physical process of unusual universality. Flow shear suppresses turbulence by speeding up turbulent decorrelation. This is a robust feature of advection whenever the straining rate of stable mean flow shear exceeds the nonlinear decorrelation rate. Shear straining lowers correlation lengths in the direction of shear and reduces turbulent amplitudes. It also disrupts other processes that feed into or result from turbulence, including the linear instability of important collective modes, the transport-producing correlations between advecting fluid and advectants, and large-scale spatially connected avalanchelike transport events. In plasmas, regions of stable flow shear can be externally driven, but most frequently are created spontaneously in critical transitions between different plasma states. Shear suppression occurs in hydrodynamics and represents an extension of rapid-distortion theory more » to a long-time-scale nonlinear regime in two-dimensional stable shear flow. Examples from hydrodynamics include the emergence of coherent vortices in decaying two-dimensional Navier-Stokes turbulence and the reduction of turbulent transport in the stratosphere. (c) 2000 The American Physical Society. « less