用偏倚缩减法检测壁湍流相干结构的时空尺度

提出了用偏倚缩减法计算壁湍流信号自相关函数，提高了自相关函数的计算精度。用壁湍流脉动速度的时间序列的自相关函数达到第二峰值对应的延迟时间检测壁湍流相干结构的平均周期。用槽道流直接数值模拟近壁区脉动速度自相关函数达到第二个峰值对应延迟长度检测壁湍流相干结构的空间平均尺度。

Detecting the Spatiotemporal Scale of Coherent Structures of Wall Turbulence by Bias Reduction Procedure

A bias reduction procedure is presented to calculate the autocorrelation function in wall turbulence. Where the average burst period of the coherent structure in wall turbulence is detected by the time delay that corresponds to the second maximum value of autocorrelation function for time series of streamwise fluctuating velocity, the average burst distance of coherent structure in wall turbulence is detected by the distance delay that corresponds to the second maximum value of autocorrelation function about streamwise fluctuating velocity in space domain.