Active Control of a Self-sustained Pressure Fluctuation due to Flow over a Cavity

Philippe Micheau, Ludovic Chatellier, Janick Laumonier, Yves Gervais
2004 10th AIAA/CEAS Aeroacoustics Conference   unpublished
The problem addressed in this paper is to control the self-sustained pressure fluctuations due to flow over a cavity. The vortex sound theory describes how sound can be induced by periodic shedding of discrete vortices at the leading edge and their interaction with the downstream edge after convection across the cavity. The pressure sound generated by the vortex-edge interaction propagates upstream and trigger the vortex shedding upstream of the leading edge. An active device can act on this
more » ... can act on this feedback loop in order to break the reinforcement mechanism, and thus to attenuate the self-sustained pressure fluctuations. The main originality of the presented active device is to use a vibrating surface located at the trailing edge in order to control the volume velocity generated by the interaction of vortex with the wall. The command of the vibrating surface is synchronized with the pressure fluctuations measured at the bottom of the cavity with a microphone. The describing function analysis is used to predict the self-sustained sinusoidal pressure and to explain the action of the active device on the feedback loop. Experimental data were obtained using the system in the test section of an Eiffel type wind-tunnel. The pressure fluctuation spectrum measured in the cavity without and with active control show an attenuation of 20 dB. Nomenclature A = Amplitude of the sinusoidal signal α = vortex concentration factor c = Sound speed, m/s * Professor, in sabbatical at LEA, Bat. K, 40 av Recteur Pineau,
doi:10.2514/6.2004-2851 fatcat:nbkz7bciqvearoe2m2lx3ugmoy