The aeroacoustics of high-lift slat under the effect of pressure fluctuations

Lo-speed wind tunnel measurements and numerical simulations of unsteady surface pressures on a wing-slat configuration are presented. The unsteady pressures are incorporated into the acoustic formulation of Lighthill & Curle to calculate the level of noise radiated into the far-field. Three main noise characteristics of the slat are identified as: 1) vortex shredding from the slat's trailing edge (high-frequency tonal noise): 2) radiation): 3 low-mid frequency noise originated from the instabilities in the shear layer inside the cove region. The vortex shredding that usually occurs at low amplitudes is a noise source that contains both dipoles and quadrupoles. The unsteady fluctuations contain dipole sources of sound and the cove region noise mechanism includes mainly mechanism ( pressure fluctuations), the effect of visco-elastic coating was investigated. It was found that the level of fluctuations was damped by almost 600 Pa, corresponding to about 3dB in noise levels.