Nonuniversal velocity probability densities in two-dimensional turbulence: The effect of large-scale dissipation
Nonuniversal velocity probability densities in two-dimensional turbulence: The effect of large-scale dissipation
复制标题
二维湍流中的非通用速度概率密度：大规模耗散的影响
DOI：
10.1063/1.3504377
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发表时间：
2010
影响因子：
4.6
通讯作者：
Y. Tsang
中科院分区：
文献类型：
--
作者：
Y. Tsang
我们发现，强迫二维湍流的一些统计特性有一个重要的敏感性的大尺度耗散的形式，这是需要阻尼的逆级联。我们考虑三种大尺度耗散模型：线性“埃克曼”阻力，非线性二次阻力，尺度选择性次阻力，阻尼低波数模式。在所有情况下，统计定常涡量场几乎由轴对称涡量主导，涡量的概率密度函数是非高斯的。然而，在线性和二次阻力的情况下，我们发现，速度统计接近高斯，与不可忽略的贡献来自背景湍流。另一方面，在次阻力的情况下，速度的概率密度函数是非高斯的，并且主要由涡的性质决定。在低阻力情况下，涡的相对位置和涡极值的指数分布是影响阻力特性的重要因素。
We show that some statistical properties of forced two-dimensional turbulence have an important sensitivity to the form of large-scale dissipation, which is required to damp the inverse cascade. We consider three models of large-scale dissipation: linear “Ekman” drag, nonlinear quadratic drag, and scale-selective hypo-drag that damps only low-wavenumber modes. In all cases, the statistically steady vorticity field is dominated by almost axisymmetric vortices, and the probability density function of vorticity is non-Gaussian. However, in the case of linear and quadratic drag, we find that the velocity statistics is close to Gaussian, with non-negligible contribution coming from the background turbulent flow. On the other hand, with hypo-drag, the probability density function of velocity is non-Gaussian and is predominantly determined by the properties of the vortices. With hypo-drag, the relative positions of the vortices and the exponential distribution of the vortex extremum are important factors respons...