Numerical Study of Aerodynamic Noise Radiated from a Three-Dimensional Wing

In this paper, a prediction method of the aerodynamic sound emitted from the three-dimensional delta wing of the attack angle at 15 degrees is presented. Computed flow Reynolds numbers range from 2.39x1 0⁵ up to 9.56X 10⁵. The method is based on the assumptions: flow Mach number is much less than unity and the strength of sound source equals Curle's dipole. These assumptions are validated by the experimental works performed in a quiet-flow-noise wind tunnel.

Owing to the low Mach number condition, the computation region can be devided into two regions: inner flow region and outer wave region. The incompressible flow computation in the inner region is performed based on the full Navier-Stokes equations. The integration of the N-S equations are executed by using finite-difference method. For high Reynolds flow computation, the nonlinear convection terms are discretized by third-order upwind difference scheme. In the outer waver region, sound emitted from the wing is predicted based on Curle's dipole equation, using calculated fluctuating pressure on the wing surface. It is found that the present method can predict the overall sound pressure level within the error of 4 dB.