Paralled DGM scheme for LEE applied to exhaust and bypass problems

Abstract

The objective of this effort is to apply the Runge-Kutta Discontinuous Galerkin Method (RK-DGM) for solving acoustic problems relevant to the aeronautics industry, like the propagation and attenuation of engine fan noise. To this end, Actran/DGM, a parallel, quadrature-free, RK-DGM has been developed to solve the linearized Euler equations in the time domain on three-dimensional, unstructured grids. The code can be used with variable orders of elements from 1 to 16; both the time step and the order of each element is automatically chosen by the code, which makes the grid generation much easier. Implementation details have been presented in previous papers. This paper presents further developments of the software package, that permit its exploitation in an industrial context for exhaust computations. A technique, already widely used in other university codes, is used to bypass the recurrent problem of the Kelvin-Helmholtz instabilities. The mean flow is directly imported from the most standard commercial CFD codes and is projected as a second order field on the acoustic mesh, which allows for coarser meshes than if the mean flow was a first order field (as it used to be in the prior version). Variants of the Munt problem are treated with Actran/DGM, assuming an expanding shear layer as proposed by Kok in the framework of the TURNEX project. The results are compared with the ones obtained by different methodologies. A realistic case is then treated with the same methodology, and a first 3D application is presented to demonstrate the feasibility of such computations.