Subsonic open cavity flows and their control using steady jets

Cavity flow induces strong flow oscillations, which increase noise, drag, vibration, and structural fatigue. This type of flow impacts a wide range of low speed applications, such as aircraft wheel wells, ground transportations, and pipelines. The objective of the current study is to examine the reverse flow interaction inside the cavity, which has a significant impact on the cavity flow oscillations. The study also investigates the impact of steady jets with different-configurations on the time-average field and the oscillations of the cavity separated shear layer. The purpose of the steady jets is suppressing the oscillations of the cavity separated shear layer. The experiments were performed for an open cavity with L/D = 4 at Reθ between 1.28×103 to 4.37×103. The steady jets were applied with different: momentum fluxes (J = 0.11 kg/m.s2,0.44 kg/m.s2 and 0.96 kg/m.s2), slot configurations (sharp edge and coanda), and blowing locations (blowing from the cavity leading and trailing edges). The data were acquired using qualitative (surface oil flow visualisation) and quantitative (hot-wire anemometry, laser Doppler anemometry, particle image velocimetry, and pressure measurements) flow diagnostics techniques. The study found that a low-frequency instability dominates the velocity spectra of the cavity separated shear layer. This instability decreases with increasing Reθ and is related to the reverse flow interaction. This interaction takes place when the reverse flow influences the sensitive separation point of the cavity separated shear layer. As a result, a large amplitude flapping wave is generated and propagates downstream of the cavity separated shear. It was also revealed that increasing J for the leading and trailing edges blowing enhances the reverse flow interaction and increases the broadband level of the unsteady wall pressure spectra. Thus, these types of jet blowing are not suitable for controlling the oscillations of the cavity separated shear layer