Leading edge noise studies using CAA

Abstract

The linearized Euler Equations were solved numerically to predict the noise, which is generated at the leading edge of a plate, when an interaction with a localized vortex takes place. One of the advantages of Computational Aeroacoustics approaches in the sense of simulating solutions to Euler's equations is, that the noise generating mechanisms become part of the simulation. Aeordynamic sound due to vorticity is generated primarily near geometric inhomogeneities, where there is usually a need to apply artificial selective damping in order to keep the numerical solution free of spurious waves of short wavelength. The local use of artificial selective damping, acting by itself as a kind of inhomogeneity, may generate unphysical noise, when interacting with vorticity. It is necessary to understand the effect of the artificial selective damping on the quality of the computed acoustic field, in order to learn, what signal to noise ratio can be expected in an aeroacoustic simulation. The effect of noise generation by artificial selective damping can be explained using acoustic wave equations and is assessed for the case of leading edge noise. The leading edge noise can be simulated correctly even if rather high values of artificial selective damping have to be employed at the sharp, infinitely thin edge.