Unsteady flow computations of a slat with a blunt trailing edge

A detailed computational study of a high lift configuration was conducted t o understand the source mechanism behind a dominant acoustic tone observed in recent experiments on slat noise. The unsteady Reynolds-averaged Navier- Stokes computations focused on accurate simulation of the local flowfield o f a slat with a blunt trailing edge. At a slat deflection angle of 30 deg r elative to the main element, the simulations revealed the presence of stron g vortex shedding behind the slat trailing edge. The resulting flow unstead iness produced large-amplitude acoustic waves propagating away from the tra iling-edge region. The local spatial resolution of the computed solution wa s sufficiently fine to capture both the near-field structure and propagatio n direction of the generated sound. The calculated shedding frequency is in good agreement with the measured acoustic frequencies obtained at NASA Lan gley Research Center's Low Turbulence Pressure Tunnel. In contrast, computa tional results at a slat deflection angle of 20 deg indicated that the shed ding process was severely damped, and, therefore, in agreement with the cor responding acoustic measurements during the experiment. There was no eviden ce of a strong acoustic source near the trailing edge at this lower slat de flection.