Identification of Coherent Structure in Turbulent Shear Flow With Wavelet Correlation Analysis

In order to identify coherent structure of turbulent shear flow, a new combination of familiar techniques of signal processing, called wavelet correlation analysis, is developed based on the wavelet transform. The wavelet correlation analysis provides the unique capability for decomposing the correlation of arbitrary signals over a two-dimensional time delay-period plane. By analyzing two superposition functions implicating several pure frequencies, the correlation of periodic oscillations at several frequencies can well be separated and observed clearly. Coherent structures in the intermediate region of a plane turbulent jet are investigated using the wavelet correlation method. It is shown that the wavelet correlation analysis can extract the most essential scales governing features of eddy motions. The coherent structure information and apparent flapping behaviors are clearly revealed over a two-dimensional time-period plane.