Two-dimensional wavelet multi-resolution analysis on turbulent structures of dune wake

Abstract

PIV experiments of dune wake were first carried out at a Reynolds number of 4660. Then two-dimensional orthogonal wavelet multi-resolution technique was applied to analyze flow structures of various scales. The instantaneous velocity and vorticity were decomposed into the large-, intermediate- and relatively small-scale components by the two-dimensional wavelet multi-resolution technique. The scale length of each wavelet component is determined by two-point autocorrelation function with the central scales of 36mm, 20mm and 12mm respectively. The turbulent kinetic energy is quantified based on multi-scale velocity. It is found that the separation region is dominated by large-scale vortical structures and its vorticity concentration makes main contribution, and the intermediate vortices in the redeveloped turbulence boundary layer lead to the breakdown process of vortical structures at the downstream of separation region. The turbulent kinetic energy is mainly contributed from the large- and intermediate-scale components, and the large-scale component makes the most contribution.