On the Small Effect of Boundary Layer Thicknesses on Slat Noise

Abstract

In landing procedure the airframe noise is comparable to the noise generated by the engines of an aircraft, being the leading edge slat one of the most important components. Experiments on slat noise generation usually are limited to much lower Reynolds numbers than those obtained in ight conditions. The present paper describes analyses made to evaluate numerically the in uence of the boundary layer thickness on the unsteady ow and noise generation at the slat cove. Time accurate simulations were done using a LatticeBoltzmann solver. Grid independence studies of the Power Spectral Density (PSD) are presented. Slat boundary layer thicknesses were found to have little in uence on turbulence and pressure spectra at the slat cove, leading to investigations of the use of free-slip walls at the slat. Very small level di erences were obtained in the slat noise produced. This assumption allowed not only a coarser grid to be employed in certain regions but also the possibility to predict slat noise in high Reynolds number ows with no major increase in simulation cost.