Isotropic third-order statistics in turbulence with helicity: the 2/15-law
Isotropic third-order statistics in turbulence with helicity: the 2/15-law
复制标题
具有螺旋性的湍流中的各向同性三阶统计：2/15 定律
DOI：
10.1017/s0022112004000424
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发表时间：
2004
影响因子：
3.7
通讯作者：
T. Matsumoto
中科院分区：
文献类型：
--
作者：
S. Kurien;Mark A. Taylor;T. Matsumoto
通过对周期区域内N-S方程的直接数值模拟，首次计算了具有螺旋度的各向同性湍流中两点三阶速度统计量的2/15定律。该定律是在惯性范围内螺旋度守恒的一种表述，类似于高雷诺数湍流中能量守恒的基准柯尔莫戈洛夫4/5定律。当在流动的任意方向上测量时，适当归一化的宇称破缺统计量与为各向同性湍流预测的2/15的理论值不一致。它们是高度各向异性和可变的，并在很长一段时间内保持不变。我们使用了一种最近开发的技术来平均多个方向，从而恢复了流动的统计各向同性分量。角度平均统计实现了2/15的系数瞬时在约7%以内，随着时间的推移平均约为5%。与能量相关的反射对称结构函数和4/5定律中的能流相比，2/15定律中的螺旋度统计和螺旋度通量的惯性和粘性量程行为更具各向异性和间歇性。这表明，在高雷诺数下局部各向同性的Kolmogorov假设需要针对这里所研究的螺旋度相关的统计数据进行修正。
The so-called 2/15-law for two-point third-order velocity statistics in isotropic turbulence with helicity is computed for the first time from a direct numerical simulation of the Navier–Stokes equations in a $512^3$ periodic domain. This law is a statement of helicity conservation in the inertial range, analogous to the benchmark Kolmogorov 4/5-law for energy conservation in high-Reynolds-number turbulence. The appropriately normalized parity-breaking statistics, when measured in an arbitrary direction in the flow, disagree with the theoretical value of 2/15 predicted for isotropic turbulence. They are highly anisotropic and variable and remain so over long times. We employ a recently developed technique to average over many directions and so recover the statistically isotropic component of the flow. The angle-averaged statistics achieve the 2/15 factor to within about 7% instantaneously and about 5% on average over time. The inertial- and viscous-range behaviour of the helicity-dependent statistics and consequently the helicity flux, which appear in the 2/15-law, are shown to be more anisotropic and intermittent than the corresponding energy-dependent reflection-symmetric structure functions, and the energy flux, which appear in the 4/5-law. This suggests that the Kolmogorov assumption of local isotropy at high Reynolds numbers needs to be modified for the helicity-dependent statistics investigated here.
影响因子：
4.6
作者：
Chen, QN;Chen, SY;Eyink, GL
通讯作者：
Eyink, GL