Coherent Structure Eduction in Wavelet-Forced Two-Dimensional Turbulent Flows

Abstract

We analyse vorticity fields obtained from direct numerical simulation(DNS) of statistically two-dimensional turbulence where the forcing is done in the wavelet space. We introduce a new eduction method for extracting coherent structures from two-dimensional turbulent flows. Using a nonlinear wavelet technique based on an objective of universal threshold we separate the vorticity fields into coherent structures and background flows. Both components are multi-scale with different scaling laws, and therefore cannot be separated by Fourier filltering. We find that the coherent structures have non-Gaussian statistics while the background flow is Gasussian, and we discuss the implications of this result in turbulence modelling