Application of a Discontinuous Galerkin Method to Predict Airframe Noise

Abstract

Unstructured grids greatly ease the mesh generation process in the case of complex geometries. The Discontinuous Galerkin Method (DGM) provides a robust, high-order accurate discretization even on this type of grid. The goal of the work reported herein is the prediction of broadband airframe noise generated by an airfoil with a deployed slat. Focus is on the noise generated by the slat, and two spatial dimensions are considered as a first step. The particularly employed DGM employs Lagrange polynomials as shape functions. They enable a simple and cheap truncation of the flux quantities of the underlying Acoustic Perturbation Equations (APE). The method is tested by computing the sound field of a monopole placed in a laminar boundary layer. Computations are stable, and very good agreement with other computations and with theoretical results is observed. Considering the prediction of broadband slat noise, the turbulent source term of the APE is computed efficiently via the stochastic FRPM (Fast Random Particle Mesh) method. Very encouraging results are obtained, and these will be analyzed in the next step.