Analysis of Aerodynamic Noise by Distributed Monopole Method.

Abstract

Aerodynamic acoustic problems near plate edges are treated by a new method based on the linear theory. For sound radiation and generation problems, we can calculate one of the half acoustic fields divided by semi-infinite plates by determining the distributions of the acoustic monopoles. Some numerical calculations confirm the validity of this distributed monopole method. Applying this method, we can impose the Kutta condition explicitly at the trailing edge and explain the feedback mechanism in terms of sound wave effects on the flow field. The generation of vorticity waves at the trailing edge due to the incident sound wave is calculated and the possibility of self-excited tones between the trailing edge and the leading edge is verified. The relationship obtained is the same as that of the edge tone phenomenon, and the necessary amplification of the vortex during its convection for the sound to become self-excited is quantified.