基于频域小波分析方法研究了大气湍流相干结构特性,采用Mexican Hat小波函数分析了近地面风速脉动数据资料。根据能量极大值原则识别相干结构主尺度,利用重构公式提取相干结构波形。结果表明重构相干波形是具有准周期运动的信号,它反映了原始脉动信号中某个中间尺度上的运动, 两者波形在变化趋势上十分吻合;小波系数的时间与尺度图可以很好地解释湍流的多尺度性和间歇性,反映了湍流相干结构的演变过程。在分析时间段内对风速相干结构的主尺度进行统计分析,发现相干结构的主尺度近似满足正态分布。

The coherent structure characteristics of atmospheric turbulence are investigated based on frequency domain wavelet analysis method. The data of wind velocity fluctuation over the ground are analyzed with Mexican Hat wavelet function. According to the maximum energy principle, the principal scale of coherent structure is identified and the coherent structure waveform is extracted by reconstruction formula. Results show that the reconstructed coherent waveform is a signal with quasi-periodic motion, which reflects a middle scale movement of the existing original pulse signal, and their waveforms coincide well with each other in the changing trend. Time and scale maps of wavelet coefficients can well explain the multi-scale and intermittence characteristics of turbulence, and reflect the evolution of turbulence coherent structure. During the analysis period, statistical analysis on the main scale of wind speed coherent structure is carried out, and it’s found that the main scale of coherent structure satisfies the normal distribution approximately.