Structure Analysis of a Turbulent Jet by Means of Multiresolution Fluctuating Velocity Decomposition

To evaluate coherent structures in the dimension of time and scale, a new procedure based on the multiresolution analysis and multiresolution auto-correlation analysis is developed in this paper. By analyzing u- and v-components of fluctuating velocity, the coherent structure and its scales can be identified when larger amplitude fluctuation and stronger autocorrelation are appeared at same wavelet level. For a turbulent jet at position of x/d = 6, the larger coherent structures with frequency 39Hz can be deduced around times 0.29, 0.53, 0.6 and 0.67s. This also represent the passing of eddies through the shear layer and concentration of the energy of the flow at these instants.