Interaction of a deformable free surface with statistically steady homogeneous turbulence
Interaction of a deformable free surface with statistically steady homogeneous turbulence
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可变形自由表面与统计稳定均匀湍流的相互作用
DOI：
10.1017/s0022112010001539
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发表时间：
2010
影响因子：
3.7
通讯作者：
Lian Shen
中科院分区：
文献类型：
--
作者：
Xin Guo;Lian Shen
对可变形自由面与底部均匀各向同性湍流之间的相互作用进行了直接数值模拟。用水平方向的拟谱方法和垂直方向的有限差分方法模拟了完全非线性自由表面边界条件下的Navier-Stokes方程。从统计学上讲，定常湍流是在下面的主体流动中使用线性强迫方法产生的。通过对不同弗劳德数和韦伯数的算例的研究，重点研究了有限幅表面变形的影响。研究发现，自由面的运动以传播波和湍流产生的表面粗糙度为特征。从速度的起伏、速度梯度和应变率的起伏以及水平和垂直湍流运动的能量平衡等方面详细分析了自由面附近湍流场的统计特性。我们的结果说明了表面堵塞和消失剪应力对流场各向异性的影响。条件平均分析表明，裂解和反裂解在组分间能量交换和垂直传输中起着重要作用。
Direct numerical simulation is performed for the interaction between a deformable free surface and the homogeneous isotropic turbulent flow underneath. The Navier–Stokes equations subject to fully nonlinear free-surface boundary conditions are simulated by using a pseudospectral method in the horizontal directions and a finite-difference method in the vertical direction. Statistically, steady turbulence is generated by using a linear forcing method in the bulk flow below. Through investigation of cases of different Froude and Weber numbers, the present study focuses on the effect of surface deformation of finite amplitude. It is found that the motion of the free surface is characterized by propagating waves and turbulence-generated surface roughness. Statistics of the turbulence field near the free surface are analysed in detail in terms of fluctuations of velocity, fluctuations of velocity gradients and strain rates and the energy budget for horizontal and vertical turbulent motions. Our results illustrate the effects of surface blockage and vanishing shear stress on the anisotropy of the flow field. Using conditional averaging analysis, it is shown that splats and antisplats play an essential role in energy inter-component exchange and vertical transport.