Visualization of Bursting Structure in a Relaminarizing Turbulent Boundary Layer Using Wavelet Analysis

Abstract

Characteristics of turbulent boundary layer with streamwise favorable pressure gradients were investigated experimentally using both the variable-interval time averaging (VITA) technique and the continuous wavelet transformation in which Gabor function was used for the analyzing wavelet. Especially, the research subject was focused on the bursting structure of the turbulent boundary layer. Results of experiments show that the Taylor's micro-time scale is the most suitable for the averaging period used in the VITA technique. Furthermore, cascade and counter cascade processes generated in the boundary layer were precisely visualized by the continuous wavelet analyses. The results show that the wavelet analysis can be one of the.most effective analyzing techniques for turbulent boundary layer investigation. On the other hand, non-dimensional bursting frequency was defined to detect the relaminarizing process of the boundary layer.