湍流相干结构与壁压强脉动关联的小波分析

Wavelet analysis of the relation between the fluctuating wall pressure and turbulent coherent structures

在风洞中同时测量平板湍流边界层的速度和壁面脉动压强,用小波分析法结合能量最大判别准则确定湍流边界层相干结构的时间尺度和壁压强脉动的时间尺度之间的关系.结果表明:压强脉动信号的小波能谱最大值对应的时间尺度与湍流边界层相干结构的特征尺度接近,可以利用壁面压强脉动信号的分析结果间接反映经过边界层的相干结构的时间特征.本研究选择复数Morlet小波作为小波母函数,有较好的分辨率.

Wavelet transform is appropriate to localized analysis in any position of a time signal for selected frequency ranges. The eddy structure can be obtained by decomposing the experimental data with scale varying, finite energy containing and localized wavelet components. Synchronous measurements of velocity and wall pressure of the turbulent boundary layer on a flat plate have been carried out in wind tunnel. The momentum thickness Reynolds numbers are 1?241 and 1?635. With the maximum energy criterion, the wavelet analysis is adopted to ascertain the relation between the scales of the coherent structures and fluctuating wall pressure of the turbulent boundary layer. The results show that the time scale corresponding to the peak value of wavelet spectra of fluctuating wall pressure is much closed to the characteristic time scale of coherent structure of the turbulent boundary layer. Therefore the analysis of time scale of fluctuating wall pressure can indicate the time features of coherent structure of the turbulent boundary layer. The complex Morlet wavelet is used, having better resolution for different scales and being appropriate to represent the time and space varying characteristics of coherent structures.