Passive Control of Cavity Flows

This paper deals with cavity flow physics and its passive control by means of a spanwise cylinder. Two configurations are considered. First, a laminar study of a flow over an unconfined square cavity at a low Reynolds number (7500) is presented. Global stability results are shown, allowing the identification of the driving mechanisms of the cavity flow: the aeroacoustic  feedback mechanism ([18]) and the acoustic resonance mechanism [4]. When both mechanisms interact, the growth rate of the global modes is seen to display a local maximum. At low Mach numbers, we suggest that it  is still the feedback aeroacoustic mechanism that selects the frequency mode, the acoustic resonance mechanism only enhancing the response. Second, we study the dynamics of a turbulent deep cavity flow in a transonic regime. Global modes and sensitivity results are shown and compared to experimental data, with and without control cylinder. Concerning the baseline (without control), RANS and URANS simulations, based on the k-ω model of Wilcox, display very good agreement with experiments. Also, the sensitivity map obtained numerically is extremely close to the experimental control map obtained by moving a small control cylinder in the usptream boundary layer and the shear-layer. Different interpretation elements are discussed.