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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Orthogonal wavelet analysis of turbulent wakes behind various bluff bodies
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Orthogonal wavelet analysis of turbulent wakes behind various bluff bodies

机译：各种钝体后的湍流尾波的正交小波分析

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摘要

The multi-scale structures of turbulent wakes generated by three kinds of bluff body, i.e. circular cylinder, square cylinder and compound of cylinder and square (CS) cylinders, have been experimentally investigated in this paper. Firstly, the instantaneous velocity fields and vorticity were measured by the high-speed PIV technique in a circulating water channel. The instantaneous streamlines and corresponding normalized vorticity contours are obtained at a Reynolds number of 5600. Then one- and two-dimensional wavelet multi-resolution technique was used to analyze the instantaneous velocities and vorticity measured by the high-speed PIV. The turbulence structures were separated into a number of subsets based on their central frequencies, which are linked with the turbulence scales. The instantaneous vorticity and Reynolds shear stresses of various scales were examined and compared between the three generators. It is found that the large-scale turbulent structure makes the largest contribution to the vorticity and Reynolds shear stresses for the three wake generators and exhibits a strong dependence upon the initial conditions or the wake generators. The large-scale vorticity and the sizes of vortex in the circular and square cylinders are larger than those in the CS cylinder wake. The contributions to the Reynolds shear stresses from the large-scale turbulent structures account for 90-96% to the measured maximum Reynolds shear stresses for the three wakes. However, the small-scale structures make less contribution to the vorticity and Reynolds shear stresses.
机译：本文通过实验研究了三种钝体产生的湍流尾流的多尺度结构，即圆柱体，方形圆柱体和圆柱体与方形圆柱体（CS）的复合体。首先，通过高速PIV技术在循环水通道中测量瞬时速度场和涡度。在雷诺数为5600时获得了瞬时流线和相应的归一化涡度轮廓。然后使用一维和二维小波多分辨率技术来分析高速PIV测量的瞬时速度和涡度。湍流结构根据其中心频率分为多个子集，这些子集与湍流尺度相关。在三个发生器之间检查并比较了各种尺度的瞬时涡度和雷诺剪切应力。发现大型湍流结构对三个尾流发生器的涡度和雷诺剪切应力贡献最大，并且表现出对初始条件或尾流发生器的强烈依赖性。圆形和方形圆柱体中的大尺度涡度和涡旋尺寸都比CS圆柱尾流中的大。大型湍流结构对雷诺剪切应力的贡献占三个尾流测得的最大雷诺剪切应力的90-96％。但是，小型结构对涡度和雷诺剪切应力的贡献较小。

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