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arXiv 1707.06809cond-mat.stat-mechhep-thphysics.flu-dyn
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各向同性和均匀turbulence中关联函数随时间变化的标度不变性的破缺

Breaking of scale invariance in the time dependence of correlation functions in isotropic and homogeneous turbulence

Malo Tarpin, Léonie Canet, Nicolás Wschebor

摘要:

本文给出了三维不可压缩流中定常、均匀和各向同性湍流统计特性的理论结果。在非微扰重整化群的框架内,我们推导出一个封闭的重整化流方程的通用$n$ -点相关(和响应)功能的大波数相对于逆积分尺度。封闭是从一个受控的扩展,并依赖于扩展的对称性的Navier-Stokes场理论。它产生的流动方程在大波数$|\vec p_i|$,并为任意的时间差$t_i$在稳定状态的确切领先的行为。进一步,我们得到了相应不动点方程的通解形式,从而得到了大波数、小$t_i$和极限$t_i\to \infty$下$n$点关联函数的超前波数和时间依赖性的解析形式.在小$t_i$下,大波数下的主导贡献在数学上等价于$-α(εL)^{2/3}|\sum t_i \vec p_i|^2$,其中$α$是非普适常数,$L$是积分尺度,$\varepsilon$是平均能量注入率。对于2点函数,已知$(t p)^2$依赖性源于扫描效应。导出的公式体现了扫频效应对$n-$点关联函数的推广。在大的波数和大的$t_i$,我们表明,$t_i^2$的依赖性在领先的订单的贡献跨越到一个$|t_i|$的依赖。在此范围内的关联函数的表达式以前没有得到,即使是2点函数。这两种预测都可以在直接数值模拟和实验中进行测试。

英文摘要:

In this paper, we present theoretical results on the statistical properties of stationary, homogeneous and isotropic turbulence in incompressible flows in three dimensions. Within the framework of the Non-Perturbative Renormalization Group, we derive a closed renormalization flow equation for a generic $n$-point correlation (and response) function for large wave-numbers with respect to the inverse integral scale. The closure is obtained from a controlled expansion and relies on extended symmetries of the Navier-Stokes field theory. It yields the exact leading behavior of the flow equation at large wave-numbers $|\vec p_i|$, and for arbitrary time differences $t_i$ in the stationary state. Furthermore, we obtain the form of the general solution of the corresponding fixed point equation, which yields the analytical form of the leading wave-number and time dependence of $n$-point correlation functions, for large wave-numbers and both for small $t_i$ and in the limit $t_i\to \infty$. At small $t_i$, the leading contribution at large wave-number is logarithmically equivalent to $-α(εL)^{2/3}|\sum t_i \vec p_i|^2$, where $α$ is a nonuniversal constant, $L$ the integral scale and $\varepsilon$ the mean energy injection rate. For the 2-point function, the $(t p)^2$ dependence is known to originate from the sweeping effect. The derived formula embodies the generalization of the effect of sweeping to $n-$point correlation functions. At large wave-number and large $t_i$, we show that the $t_i^2$ dependence in the leading order contribution crosses over to a $|t_i|$ dependence. The expression of the correlation functions in this regime was not derived before, even for the 2-point function. Both predictions can be tested in direct numerical simulations and in experiments.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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