Wavelet Analysis of Unsteady Shock-wave Motion on Two-dimensional Airfoil with Vortex Generators
Toshinori Kouchi, Shingo Yamaguchi, Shunsuke Koike, Shinichiro Yanase, Tsutomu Nakajima, Mamoru Sato, Atsushi Kanda · 54th AIAA Aerospace Sciences Meeting · 2016
We visualized the shock wave-boundary layer interaction on a two-dimensional transonic airfoil with and without vortex generators (VGs) by using a fast-framing focusing schlieren imaging. Image processing extracted a time-space trajectory of the shock wave motion from a time-series of the schlieren images. The shock trajectories were analyzed by using the Morlet wavelet. The shock motions in the cases without VGs were quite periodic. The Fourier analysis well extracted the characteristics of the shock motion such as frequency etc. However, the shock motions in the cases with VGs were not periodic. Therefore, the Fourier analysis is not applicable for this case. The wavelet analysis with the statistical significance test gave quantitative measure of change in the shock oscillation around the buffet frequency due to installation of VGs, such as amplitude and intermittency. The wavelet spectrograms revealed that the installation of VGs did not prevent from generating the buffet but just reduced the amplitude of the buffet oscillation.