Evaluation and development of non-reflective boundary conditions for aeroacoustic simulations

The performance of several non-reflective acoustic boundary conditions is quantitatively compared using a plane wave test configuration. The study uses a high-order linearized Euler equation solver to find a non-reflective boundary condition which gives good performance in a variety of cases. The performance for acoustic waves with varying frequency and incident angle is compared in flows with varying Mach number. The performance of buffer zone, far-field, and characteristic non-reflective methods is compared. Some non-reflective boundary methods, such as buffer zones, contain tuneable parameters that are optimized in the current work. This provides a more comprehensive evaluation than previous studies which used constant values of the tuneable parameters. A new generic non-reflective zonal characteristic boundary condition is proposed and is shown to give improved performance in comparison to other tested methods. The performance of the proposed boundary condition is also demonstrated in a two-dimensional airfoil turbulence-interaction case that includes vortical waves leaving the domain, and in a three-dimensional duct mode case.