Aerodynamic Noise Induced by Laminar and Turbulent Boundary Layers over Rectangular Cavities

Abstract

The structure of an unsteady o w past a rectangular, open cavity is investigated using numerical simulations. Particular attention is drawn to the three-dimensional geometry eects, and to the turbulent state of the incoming boundary layer. The consequences on noise generation are studied. Two-dimensional DNS allows a reconstruction of the feedback loop giving rise to the selfsustained oscillations, but DNS is restricted to thick laminar upstream boundary layers. Cavity o ws with higher Reynolds numbers are computed by 3-D Large Eddy Simulations, based on high order algorithms, by considering that the interactions of coherent structures with the downstream edge are predominant in such o ws. The three-dimensional structure of the recirculating zone is illustrated and its inuence on the shear layer dynamics is shown . In the same way as the incoming turbulence level, these modulations induce jittering of vortex-corner interactions, a decrease in feedback coherence, and thus a reduction of the radiated noise.