Efficient interfacing scheme for using source terms in a high-order DG aeroacoustics propagation solver

For low Mach number problems, hybrid computational aeroacoustics (CAA) methodologies are commonly considered as the most appropriate technique for numerical simulation of aerodynamically generated noise and their far-field propagation with reasonable computational effort. In a hybrid CAA-approach, the final acoustic radiation field is obtained through a three-step procedure. At first, the aerodynamic noise generating mechanisms are obtained using an unsteady flow simulation. Secondly, the mean flow variables and source terms are calculated, and the resulting data is mapped from the CFD mesh to the acoustic propagation mesh. Finally, the acoustics propagation is performed. Since the dominating acoustic wavelengths for high Reynolds and low Mach numbers flows are much larger than the size of the aerodynamic features, the CFD grid is significantly more refined than the acoustic grid. However, when the problem is characterized by strong gradients that are under-resolved by the high order polynomial representation on the DG elements, spurious oscillations may occur (Runge's phenomena). To overcome this, a flexible interfacing scheme for the mapping between the two meshes is developed. The adopted approach uses a global least square procedure for continuous mapping in combination with an additional anti-aliasing filtering. Furthermore, the approach is meshless, thus information on the CFD grid topology is not required. The performance of the proposed technique is studied for the well documented spinning vortices benchmark problem. For this case, the sources of sound can be numerically generated, avoiding the long computational time that normally comes with the use CFD techniques. Finally, for the acoustic propagation, a high-order discontinuous Galerkin (DG) solver is used to solve the linearized Euler equations (LEE).Book subtitle: MAJOR CHALLENGES IN ACOUSTICS, NOISE AND VIBRATION RESEARCH, 2015status: publishe