Combined soft-threshold wavelet de-noising with MRA on the detection of turbulent coherent structure

Coherent structure is a quasiperiodic large-scale structure and plays an important role in the generation, dissipation, and transfer energy in turbulent flow. One of the problems in the research on turbulence is how to extract coherent structure from physical or numerical experiment quantificationally. Wavelet transform has been used as a new method to recognize coherent structure in turbulent flow (Farge 1996). Because coherent structure embodies the maximum energy among all eddy structures of turbulence, we can perform multiresolution analysis to turbulent signal, and taking the scale that contains maximum energy as the scale of coherent structure. In this paper, we analyze the scale of coherent structure by multiresolution analysis according to the maximum energy criteria, and present a new soft threshold wavelet de-noising method suitable for turbulent signal to eliminate the noise in the scale of coherent structure. In the end, coherent structure is detected and extracted from turbulent signal.