Y. Reymen, 3D high-order discontinuous Galerkin methods for time-domain simulation of flow noise propagation, 2008

Abstract

The direct approach to aeroacoustics, solving the Navier-Stokes equations at a high resolution and for a large domain, is computationally expensive. An alternative approach, the hybrid technique, splits the computation in two parts: a flow and sound generation part and a subsequent propagation part. This allows to choose optimal discretizations and domain sizes for each part, reducing the total cost.

This dissertation focusses on the development of an accurate and flexible tool for the propagation part, capable of dealing with complex geometries. The Linearized Euler Equations (LEE) are the model equations and allow to simulate the propagation of acoustic waves in the presence of a (non-uniform) mean flow, accounting for convection and refraction effects. Special attention is paid to the modelling of wall damping treatment.

The Discontinuous Galerkin method in its quadrature-free form is used to discretize the LEE. This is a very compact method, suited for high-order simulations on unstructured grids of hexahedra or tetrahedra. Parameter studies are performed studying the influence of element size, element order, grid topology and grid regularity. The directivity of the errors is explored.

A new and efficient time-domain impedance formulation is given to model wall damping treatment. A generic frequency model enables to represent broadband impedance; recursive convolution provides an efficient translation of that model to time-domain. A dedicated model for single-frequency simulations is given that allows to enforce the exact impedance at a design frequency.

Order Code

Code: 08D10