Abstract
To evaluate coherent structures in the dimension of time and scale, a definition of wavelet multiresolution autocorrelation based on the discrete wavelet transform is first developed. Then a new identification technique that combines the wavelet multiresolution analysis combined with the wavelet multiresolution autocorrelation analysis is proposed. By analyzing u- and v-components of fluctuating velocity, the coherent structure and its scales can be identified when larger local amplitude fluctuation and stronger autocorrelation appear at the same wavelet level. For a turbulent jet at a downstream distance of x/d=6, the coherent structures with frequency 39Hz can be deduced about times 0.29, 0.53, 0.6, and 0.67s. This also represents the passing of eddies through the shear layer and concentration of the energy of the flow at these instants.
