Wavelet analysis of detecting multi-scale coherent structures and intermittency in wall turbulence
Tian Yan · Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University · 2005
The velocity time sequence at different vertical locations were finely measured by hot wire anemometer. A conditional sampling technique for detecting multi-scale coherent structures was developed using instantaneous intensity factor and flatness factor of wavelet coefficients. Multi-scale coherent structures for different scales were extracted by this technique.The probability density function(PDF) was calculated using wavelet coefficients, and the influence of multi-scale coherent structures on PDF was also studied. Multi-scale coherent structure evolution shapes detected at different scales were found to be similar. They are responsible for the anomalous scaling law. When such events are eliminated, intermittency anomalies are no longer observed and the Gauss normal distribution is achieved on the PDF of wavelet coefficients.