On the role of the laminar/turbulent interface in energy transfer between scales in bypass transition
On the role of the laminar/turbulent interface in energy transfer between scales in bypass transition
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DOI：
10.1017/jfm.2023.194
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发表时间：
2022-07
影响因子：
3.7
通讯作者：
H. Yao;G. Papadakis
中科院分区：
文献类型：
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作者：
H. Yao;G. Papadakis
本文利用KHMH方程研究了层流/湍流界面在边界层旁路转捩中尺度间能量传递的作用。局部二进制指示函数用于检测界面，随后用于定义两点插值。这些被用来分解成有条件的平均分量的标准平均的尺度间和空间能量通量。我们发现，逆叶栅在流向的早期工作报告中出现的事件，由于跨下游或上游界面的湍流斑点。然而，三维能通量图显示这两个区域之间的显着差异：在下游界面，逆叶栅是更强的，占主导地位的流向和展向分离的范围更大。我们解释了这一发现，考虑传播点的简化形状，因为它穿过一个固定的流向位置。我们还推导出条件平均KHMH方程，从而将类似的单点统计方程推广到两点统计。我们比较了三维地图的条件平均生产和总能量通量的湍流斑点对地图的标准平均量内的完全湍流区域。结果表明，湍流斑和完全湍流区的两点统计显着的动力学相似性。这是已知的，只有单点量，我们在这里证明，相似性扩展到两点量以及。
Abstract We investigate the role of the laminar/turbulent interface in the interscale energy transfer in a boundary layer undergoing bypass transition with the aid of the Kármán–Howarth–Monin–Hill (KHMH) equation. A local binary indicator function is used to detect the interface and employed subsequently to define two-point intermittencies. These are used to decompose the standard-averaged interscale and interspace energy fluxes into conditionally averaged components. We find that the inverse cascade in the streamwise direction reported in an earlier work arises due to events across the downstream or upstream interfaces of a turbulent spot. However, the three-dimensional energy flux maps reveal significant differences between these two regions: in the downstream interface, inverse cascade is stronger and dominant over a larger range of streamwise and spanwise separations. We explain this finding by considering a propagating spot of simplified shape as it crosses a fixed streamwise location. We derive also the conditionally averaged KHMH equation, thus generalising similar equations for single-point statistics to two-point statistics. We compare the three-dimensional maps of the conditionally averaged production and total energy flux within turbulent spots against the maps of standard-averaged quantities within the fully turbulent region. The results indicate remarkable dynamical similarities between turbulent spots and the fully turbulent region for two-point statistics. This has been known only for single-point quantities, and we demonstrate here that the similarity extends to two-point quantities as well.