Mode-switching and nonlinear effects in compressible flow over a cavity

摘要: Multiple distinct peaks of comparable strength in unsteady pressure autospectra often characterize compressible flow-induced cavity oscillations. It is unclear whether these different large-amplitude tones (i.e., Rossiter modes) coexist or are the result a mode-switching phenomenon. The cause additional spectrum, particularly at low frequency, also unknown. This article describes analyses data using time-frequency methods, namely short-time Fourier transform (STFT) and continuous Morlet wavelet transform, higher-order spectral techniques. STFT clearly show that dominant mode switches between primary modes. verified by instantaneous schlieren images acquired simultaneously with pressures. Furthermore, modes experience some degree low-frequency amplitude modulation. An estimate modulation obtained from analysis, matches low-fr...