Phase Averaging on Square Cylinder Wake Based on Wavelet Analysis

Abstract

Phase average techniques based on wavelet multiresolution analysis and continuous wavelet transform are developed to reveal the phase-averaged features of square cylinder wake measured by high-speed PIV. The multi-scale turbulent structures are phase-sorted to give phase-averaged representations of flow field. The phase-averaged measured flow fields suggest that the wake flow rolls up and down and is conveyed downstream together with the corresponding vortices, forming a vortex pair with opposite sense of rotation. The phase-averaged vorticity contours of large-scale flow structures show good correspondence to the topology of phase-averaged measured flow field, suggesting the alternative nature of the vortex street with strong periodicity. The phase averaged intermediate-scale structures tend to be conveyed downstream along streamwise direction, with the rotation sense vary from the first half period to the last half period, implying the nature of Kelvin-Helmholtz vortex.