Structure Identification of the Turbulent Flow Using the Continuous Wavelet Transform
6 Pages Posted: 16 Apr 2019 Last revised: 29 May 2019
Date Written: April 27, 2019
The continuous wavelet transform (CWT) is an interesting way to obtain, at the same time the signal decomposition in space and time. It can detect and analyze the coherent structures which are formed out of turbulent flows. In the present work, we firstly perform a Fourier spectral analysis of the velocity field, obtained experimentally of a turbulent wall jet over a backward facing step in the recirculation zone, considering two different instants of its evolution. It can be noted that the energy is distributed almost on all the frequencies; therefore, the flow is in a non-equilibrium state, which means the presence of coherent structures (supposed to be responsible for intermittency). Secondly, we identify these coherent structures, by applying the one-dimensional CWT, using the Mexican hat wavelet. The data analysis shows that the smallest scales are located more over time by focusing on the centers of the coherent structures.
Keywords: Continuous Wavelet Transform, Coherent Structures, Mexican Hat Wavelet, Turbulent Flow, Wall Jet
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