Recent Development of Non-Linear Aeroacoustic Model for Wind Turbine Computations

A numerical algorithm for simulation of acoustic noise generation, based on collocated grids, has been developed.The approach, that was originally developed using a viscous/inviscid decomposition technique, involved two steps comprising a viscous incompressible flow part and an inviscid acoustic part.

On collocated grids the inviscid solution is found to be mesh dependent due to unavoidable extrapolations of the acoustic pressure and density at walls, differing from the case on staggered grid where no extrapolation is needed. The situation is most pronounced when a sharp body is considered.A viscous acoustic algorithm is proposed to overcome the difficulty.

The model is currently applied to the problem of an airfoil exposed to a gust and results are compared to the numerical results of Lockard and Morris [AIAA J. 36(6) (1998) 907].