Large-scale structure of velocity and passive scalar fields in freely decaying homogeneous anisotropic turbulence
Large-scale structure of velocity and passive scalar fields in freely decaying homogeneous anisotropic turbulence
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自由衰减均匀各向异性湍流中速度场和被动标量场的大尺度结构
DOI：
10.1103/physrevfluids.3.104601
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
K. Yoshimatsu and Y. Kaneda
中科院分区：
文献类型：
--
作者：
Liu Jijun;Machida Manabu;Nakamura Gen;Nishimura Goro;Sun Chunlong;K. Yoshimatsu and Y. Kaneda
本文考虑自由衰减的均匀各向异性湍流，其能量谱在初始时刻由给出，其中是波数，是一个独立的正数。一个参数给出表明，有一个无限数量的不变量表征的大尺度结构的湍流。这是Saffman论证的一个推广，它表明存在有限个不变量[P.G. Saffman，J. Fluid Mech.27，581（1967）JFLSA70022-112010.1017/S0022112067000552]。通过应用类似的参数均匀各向异性被动标量湍流没有任何标量源，我们表明，有一个无限数量的不变量表征被动标量场的大尺度结构。基于大尺度演化的不变性和自相似性假设的理论分析表明，速度场和被动标量场的各向异性在大尺度上是持久的。通过简单的量纲分析，推导出速度场和无源标量场的衰减规律。
We consider freely decaying homogeneous anisotropic turbulence whose energy spectrumatis given byat an initial instant, whereis the wave number andis a-independent positive number. An argument is given to show that there are an infinite number of invariants characterizing the large-scale structure of the turbulence. This is a generalization of Saffman's argument, which shows the existence of a finite number of invariants [P. G. Saffman, J. Fluid Mech. 27, 581 (1967)JFLSA70022-112010.1017/S0022112067000552]. By applying a similar argument to homogeneous anisotropic passive scalar turbulence without any scalar source, we show that there are an infinite number of invariants characterizing the large-scale structure of passive scalar fields. Theoretical analysis based on the invariance and a self-similarity assumption for the large-scale evolution shows that the anisotropy of the velocity and passive scalar fields is persistent at large scales. The decay laws of the velocity and passive scalar fields are derived by a simple dimensional analysis.