Self-sustained oscillation for compressible cylindrical cavity flows

The presence of a cavity changes the mean and fluctuating pressure distributions.Simi larities are observed between a cylindrical cavity and a rectangular cavity for a compressible flow.The type of cavity flow field depends on the diameter-to-depth ratio and the length-to-depth ratio.The feedback loop is responsible for the generation of discrete acoustic tones.In this study,the selfsustained oscillation for a compressible cylindrical cavity flow was investigated experimentally.For open-type cavities,the power spectra show that the strength of resonance depends on the diameter to-depth ratio (4.43-43.0) and the incoming boundary layer thickness-to-depth ratio (0.72-7.0).The effective streamwise length is used as the characteristic length to estimate the Strouhal number.At higher modes,there is a large deviation from Rossiter's formula for rectangular cavities.The gradient-based searching method was used to evaluate the values of the empirical parameters.Less phase lag and a lower convection velocity are observed.