The energy cascade in near-field non-homogeneous non-isotropic turbulence
The energy cascade in near-field non-homogeneous non-isotropic turbulence
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DOI：
10.1017/jfm.2015.201
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发表时间：
2015-05-01
影响因子：
3.7
通讯作者：
Vassilicos, J. C.
中科院分区：
文献类型：
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作者：
Gomes-Fernandes, R.;Ganapathisubramani, B.;Vassilicos, J. C.
我们在网格产生湍流的最不均匀和各向异性区域，即网格和湍流强度峰值之间的产生区域，对非齐次卡门-豪沃斯-莫宁方程的各项进行了粒子图像测速（PIV）测量。我们使用一个有据可查的分形网格，它被认为可以放大生产区域的流向范围，并减弱其湍流活动。在该区域中心周围的中线上，两点平流和输运项占主导地位，生产也很显著。因此，不可能应用基于Karman-Howarth-Monin方程和由此产生的量纲考虑的通常Kolmogorov参数来推导尺度间通量和光谱性质。这个位置的尺度间能量传递是高度各向异性的，由不同方向的正级联和逆级联组成，当在方向上平均时，得到一个负的尺度间能量通量（因此平均为正级联），并且在r（两点之间的分离向量r的模量）上离线性不远。流向波动分量的能谱在10年内表现出明确的-5/3幂律，即使流向与反级联方向的角度很小。
We perform particle image velocimetry (PIV) measurements of various terms of the non-homogeneous Karman-Howarth-Monin equation in the most inhomogeneous and anisotropic region of grid-generated turbulence, the production region which lies between the grid and the peak of turbulence intensity. We use a well-documented fractal grid which is known to magnify the streamwise extent of the production region and abate its turbulence activity. On the centreline around the centre of that region the two-point advection and transport terms are dominant and the production is significant too. It is therefore impossible to apply usual Kolmogorov arguments based on the Karman-Howarth-Monin equation and resulting dimensional considerations to deduce interscale flux and spectral properties. The interscale energy transfers at this location turn out to be highly anisotropic and consist of a combined forward and inverse cascade in different directions which, when averaged over directions, gives an interscale energy flux that is negative (hence forward cascade on average) and not too far from linear in r, the modulus of the separation vector r between two points. The energy spectrum of the streamwise fluctuating component exhibits a well-defined -5/3 power law over one decade, even though the streamwise direction is at a small angle to the inverse cascading direction.