Analysis of interscale energy transfer in a boundary layer undergoing bypass transition
Analysis of interscale energy transfer in a boundary layer undergoing bypass transition
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旁路跃迁边界层中的尺度间能量传递分析
DOI：
10.1017/jfm.2022.285
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发表时间：
2022
影响因子：
3.7
通讯作者：
G. Papadakis
中科院分区：
文献类型：
--
作者：
H. Yao;J. Mollicone;G. Papadakis
摘要利用Kármán-Howarth-Monin-Hill方程研究了自由流湍流引起的旁路转捩边界层的产生和尺度间能量传递。计算了覆盖层流、过渡流和湍流流态的不同长度尺度的能量通量。比例能量生产和通量矢量的地图在二维平面和三维超平面上可视化，包括物理空间和分离空间。在过渡区，在靠近壁面的顺流方向显示出强烈的逆级联。能量通量矢量来自强生产和向更大的流尺度转移能量的区域。为了更深入地了解反叶栅过程的起源，我们将能量通量矢量分解为由速度波动、平均流动不均匀性、压力和粘性效应之间的非线性相互作用产生的分量。反级联主要是非线性相互作用分量造成的，在过渡的最初阶段，非线性相互作用分量与平均流动不均匀性分量竞争。通过叠加瞬时速度场和能量通量矢量，我们将反级联过程与湍流斑的生长联系起来。一旦过渡过程完成，这些图就变得与在其他充分发展的湍流中观察到的非常相似，例如水道流。最后，我们用概率密度函数（pdf）来描述非线性相互作用项。在均匀各向同性湍流中，pdf是不对称的和宽裙边的，但向正值倾斜，反映了反级联。
Abstract The Kármán–Howarth–Monin–Hill equation is employed to study the production and interscale energy transfer in a boundary layer undergoing bypass transition due to free-stream turbulence. The energy flux between different length scales is calculated at several streamwise locations covering the laminar, transitional and turbulent regimes. Maps of scale energy production and flux vectors are visualised on two-dimensional planes and three-dimensional hyper-planes that comprise both physical and separation spaces. In the transitional region, the maps show strong inverse cascade in the streamwise direction near the wall. The energy flux vectors emanate from a region of strong production and transfer energy to larger streamwise scales. To provide deeper insight into the origin of the inverse cascade process, we decompose the energy flux vector into components arising from nonlinear interactions between velocity fluctuations, mean flow inhomogeneity, pressure and viscous effects. The inverse cascade is mainly due to the nonlinear interaction component, and in the earliest stages of transition this component competes with that due to mean flow inhomogeneity. By superposing the instantaneous velocity fields and the energy flux vectors, we relate the inverse cascade process to the growth of turbulent spots. Once the transition process is complete, the maps become very similar to those observed in other fully developed turbulent flows, such as channel flow. Finally we characterise the nonlinear interaction term using probability density functions (PDFs) evaluated at different wall-normal heights. The PDFs are asymmetric and wide-skirted as in homogeneous isotropic turbulence, but are skewed towards positive values reflecting the inverse cascade.
影响因子：
3.7
作者：
A. Cimarelli;J. Mollicone;M. van Reeuwijk;E. De Angelis
通讯作者：
A. Cimarelli;J. Mollicone;M. van Reeuwijk;E. De Angelis
影响因子：
3.7
作者：
F. Alves Portela;G. Papadakis;J. Vassilicos
通讯作者：
F. Alves Portela;G. Papadakis;J. Vassilicos
影响因子：
3.7
作者：
F. A. Portela;G. Papadakis;J. C. Vassilicos
通讯作者：
F. A. Portela;G. Papadakis;J. C. Vassilicos