Computation of aerodynamic noise emitted from a door mirror of a passenger car and its synthesis

The aerodynamic noise caused by an outside door mirror of a passenger car was calculated and synthesized. Flows around the car including the mirror were computed using a finite-difference method and an overlapping grid technique. Sound pressure of the aerodynamic noise in far field from the car was computed with Curie's formula using unsteady pressure distribution on the mirror which is numerically solved from the incompressible Navier-Stokes equations. The sound is then synthesized for engineers to evaluate. We investigate the relation between noise sources and the flow field, and find that the strong noise sources are distributed along sepalation lines. This means it possible to reduce the noise if we can avoid separation or fix sepalation lines. Considering it, we modified the mirror shape and succeeded to reduce the aerodynamic noise.