C. Maury, T. Bravo and D. Mazzoni
The 48th International Congress and Exhibition on Noise Control Engineering. INTERNOISE 2019.
Del 16 al 19 de junio de 2019, Madrid, España.
Experimental studies have been carried out to assess the effect on the pressure fluctuations of micro-perforating the base wall of cavities mounted in a low-speed wind-tunnel and undergoing a fully-developed turbulent boundary layer. Measurements in transitional- and closed-flow regimes showed a reduction by up to 8 dB of the dominant tonal peaks in the base wall-pressures. These peaks occur on one-third of the cavity floor towards the leading edge. They are identified as transverse tunnel-cavity resonances excited by the shear layer and coupled with the thin panel flexural modes. However, the micro-perforations are inefficient downstream of the attenuation zone to attenuate the broadband pressure fluctuations. Two-dimensional Lattice-Boltzmann simulations were performed for a transitional cavity mounted in a waveguide and undergoing a low-speed boundary layer. The calculated wall pressure spectra confirmed the existence of transverse tunnel-cavity resonances as well as their attenuation at the base and at the mouth of the cavity by inserting a micro-perforated floor. In particular, the dissipation of energy is concentrated within and at the inlet-outlet of the base-wall apertures which correspond to regions of maximum velocity fluctuations.
ACKNOWLEDGEMENTS This work has been funded by The Ministerio de Economía y Competitividad in Spain, project TRA2017-87978-R, AEI/FEDER, UE, “Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad”. It was supported in France by the Labex Mechanics and Complexity AAP2 managed by the Excellence Initiative Programme of Aix-Marseille University (A*MIDEX).
