Large-scale flow generation by inhomogeneous helicity.
Large-scale flow generation by inhomogeneous helicity.
复制标题
通过不均匀螺旋度产生大规模流动。
DOI：
10.1103/physreve.93.033125
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Axel Brandenburg
中科院分区：
文献类型：
--
作者：
N. Yokoi;Axel Brandenburg
研究了运动螺旋度(速度-涡度关联)对湍流动量输运的影响。湍流运动螺旋度(伪标量)以螺旋度梯度的形式进入雷诺应力(镜像对称张量)表达式，作为平均涡度和/或角速度(轴向量)的耦合系数，这表明在存在非均匀螺旋度的情况下可能产生平均流。这种非均匀螺旋度效应以前是在湍流或闭合模型模拟的水平上被证实的，本文借助于外部强迫所支持的具有非均匀螺旋度的旋转湍流的直接数值模拟来研究这种非均匀螺旋度效应。数值模拟表明，雷诺应力的空间分布与螺旋度相关项与角速度的耦合一致，在角速度方向上产生了大尺度流动。在均匀湍流螺旋度的情况下，不会引起如此大尺度的流动。这一结果证实了非均匀螺旋度效应在大尺度流动产生中的有效性，并表明即使在不存在斜压性效应的不可压缩湍流中，涡旋发电机也是可能的。
The effect of kinetic helicity (velocity-vorticity correlation) on turbulent momentum transport is investigated. The turbulent kinetic helicity (pseudoscalar) enters the Reynolds stress (mirror-symmetric tensor) expression in the form of a helicity gradient as the coupling coefficient for the mean vorticity and/or the angular velocity (axial vector), which suggests the possibility of mean-flow generation in the presence of inhomogeneous helicity. This inhomogeneous helicity effect, which was previously confirmed at the level of a turbulence- or closure-model simulation, is examined with the aid of direct numerical simulations of rotating turbulence with nonuniform helicity sustained by an external forcing. The numerical simulations show that the spatial distribution of the Reynolds stress is in agreement with the helicity-related term coupled with the angular velocity, and that a large-scale flow is generated in the direction of angular velocity. Such a large-scale flow is not induced in the case of homogeneous turbulent helicity. This result confirms the validity of the inhomogeneous helicity effect in large-scale flow generation and suggests that a vortex dynamo is possible even in incompressible turbulence where there is no baroclinicity effect.