CAA-RPM prediction and validation of slat setting influence on broadband high-lift noise generation

Abstract

Broadband sound generated at the slat of a three-element high-lift wing is simulated with a CAA method. Especially, the effect of different slat and gap settings is studied and the results are validated with measurements. The applied method rests on the use of steady Reynolds Averaged Navier-Stokes (RANS) simulation to prescribe the time-averaged motion of turbulent flow. By means of synthetic turbulence generated with the Random Particle-Mesh (RPM) method the steady one-point statistics (e.g. turbulent kinetic energy) and turbulent length- and time-scales of RANS are translated into fluctuations with statistics that very accurately reproduce the spatial target distributions of RANS. The synthetic fluctuations are used to prescribe sound sources which drive linear acoustic perturbation equations. The whole approach represents a methodology to solve statistical noise theory with state-of-the-art Computational Aeroacoustics (CAA) tools in the timedomain. The comparison with experiments are conducted for four selected settings, chosen from a matrix comprising in total 43 individual slat-gap and overlap combinations. CAA simulations are performed for all matrix positions. The CAA computations are obtained as blind predictions prior to the measurements conducted in the AWB wind tunnel. Good agreement of the noise trends are found between CAA and experiments. The difference in level between the selected configurations is obtained qualitatively and quantitatively by CAA.