壁湍流标度律与流动结构实验分析

Experimental analysis of the scaling law and the flow structure in turbulent boundary layer

标度律是研究湍流统计和湍流级串的重要工具,文中应用PIV系统的分辨率较高和帧率较高的特点,对在动量损失厚度雷诺数Reθ=2 694时实验区域的脉动速度数值进行测量,利用统计学和小波分析的方法对SL标度律的间歇参数和最奇异标度指数进行拟合分析.从结果中可看出,SL标度律的间歇参数并不是一个固定的数值,而是和尺度的大小及壁面位置有关;SL标度律的另一个参数最奇异标度指数是随着壁面距离和尺度的增大趋于稳定,在大尺度上与壁面的距离无关.小波分析重构前后的流动图案显示也验证了湍流的级串过程及标度律运算的正确性.

As a universal principle of turbulence cascade,scaling law is important in the research on statistics of turbulence. In the thesis PIV system has been used to measure the fluctuating velocity in order to analyze the parameters（ the intermittence factor and the exponent of the most intermittent structure） of SL scaling law in boundary layer at Reθ= 2 694. The method of wavelet and statistics have been used in this paper. At different distances from the wall and different scale,the results show the intermittence factor is changeable. However,with rising the distance from wall and scale,the exponent of the most intermittent structure tends to be stable. When the scale is big enough,the exponent of the most intermittent structure doesn＇t relate to the distances from the wall.The original graph and the picture of wavelet reconstruction demonstrate the process of turbulent cascade and correctness of the scaling law.