Acoustic field around a transonic cavity flow

This paper describes new techniques for analysing cavity flows. The beamforming method is used to estimate the pressure fluctuations inside a resonant transonic cavity, highlighting the localisation of the sources of noise. The method produces insightful results and only requires the use of an acoustic array and a mean flow-field. The technique models the noise propagation in a simple and efficient way, applicable for wind tunnel test. In addition, this paper discusses the generation of the cavity tones. Computational fluid dynamics results are analysed using a superposition of reflected acoustic waves driven by the cavity flow. This analysis shows that the time-averaged flow-field drives the frequencies of the tones, while the flow-field fluctuations drive their amplitude. In addition, the tonal dynamics of the cavity flow are represented by a simple model with standing wave oscillations and their modulation. This work is complementary to the well-established Rossiter cavity model.