Investigation of the Unsteady Flow and Noise Generation in a Slat Cove

This study presents hybrid Reynolds-averaged Navier -Stokes/large-eddy simulations of the unsteady flow and noise-generation phenomena in the slat cove of a high-lift wing profile. These computations are part of a joint numerical/experimental aeroacoustics collaborative program dedicated to slat-flow analysis. A dedicated two-element wing profile (slat plus main body) has been designed to isolate slat noise from other possible sources (e.g., the flap), while minimizing mean flow deflection effects, to improve the fidelity of open-jet wind-tunnel measurements. The design of this two-element airfoil has been performed numerically, using an optimization process based on steady Reynolds-averaged Navier -Stokes calculations. This airfoil has been investigated experimentally at the cole Centrale de Lyon open jet facility. Unsteady zonal hybrid Reynolds-averaged Navier -Stokes/ large-eddy simulations have been performed to provide a comprehensive description of the unsteady flow inside the slat cove, focusing on the noise-generation processes. A detailed analysis of the physics of the unsteady flow inside the slat cove is presented as well as a comparison of numerical results with available experimental data. The pressure spectra associated with the slat-cove flow are characterized by several tonal peaks emerging from the underlying broadband content. The existence of such peaks is attributed to a feedback loop involving the main shear layer inside the slat cove. A theoretical law is proposed to predict the associated tonal frequencies and assessed at the end of the paper.