Abstract:

This paper describes a new method for predicting high speed impulsive noise generated by a hovering rotor blade. The nonlinear near field solution is computed by an Euler solver, and the pressure signal in the near field can be extracted directly from the Euler solution; moreover,the sound propagation to the far field is computed with linear acoustic methods, namely, the Kirchhoff integration over a surface that completely encloses the rotor blades. Although lacking experimental verification at this time, the results of computed high speed impulsive noise are promising. These calculations show that some benefit can be obtained by taking thin or sweep or taper blade tip shape in reducing the far field noise. Overall, the combined Euler/Kirchhoff scheme provides a powerful new framework for engineering purposes of noise prediction.

Key words: rotor, aeroacoustics, Kirchhoff method, CFD, helicopter