子波变换在实验流体力学中的应用

介绍了子波分析的历史、基本知识以及在实验流体力学方面的应用。讨论了子波变换在客观辨识湍流边界层相干结构方面的应用。作者用子波变换的方法提出了确定湍流边界层相干结构挥发时间尺度的能量最大准则，提取了相干结构对应的速度信号波形。用于波变换研究了湍流边界层脉动速度信号的局部奇异性行为，发现相干结构发生处脉动速度信号的局部奇异性指数为负值。

WAVELET TRANSFORM APPLICATIONS TO EXPERIMENTAL FLUID MECHANICS

This paper is a simple survey about wavelet transformation. A note of its history,basic knowledge is introduced and its applications to experimental fluid mechanics are exhibited. The wavelet transform is used to perform the time-frequency double local decomposition in time space and frquency space for the hot-film anemometer output signal of the stteamwise velocity fluctuation in turbulent boundary layer over a smooth flat surface. The energy evolution of the turbulent fluctuating velocity across scales is studied from the wavelet coefficients. The energy maxima criterion is presented to determined the time scale related to the coherent structure burst events in boundary layer turbulence. The velocity signal that corresponds to coherent structures is extracted from the fluctuating signal. The local singularity behavior of fluctuating velocity in boundary layer turbulence is studied using the wavelet transform. It is found that the local singular exponent is negative when the coherent structure burst occurs.