Accurate CAA-Simulations using a Low-Mach Aerodynamic/Acoustic Splitting Technique

Hybrid CAA-approaches are commonly used for aero-acoustic engineering applications. For these kinds of numerical techniques, the computational domain is split into a noise generating region, where an aerodynamic field generates the aeroacoustic sources, and an acoustic propagation region. In this way, domain decomposition enables the use of different equations, computational grids and numerical techniques, thus improving the overall numerical efficiency. A crucial step for these hybrid methodologies is the determination of accurate coupling information from the unsteady aerodynamic simulation. In order to obtain more accurate results, an aerodynamic/acoustic splitting procedure is needed when compressible effects inside the source region are non-negligible or when acoustic results inside a turbulent flow region are required. For this purpose, a low-Mach number splitting is developed and validated for the application of both the aerodynamic noise generation by the flow over a square cylinder and the noise emitted by a rectangular cavity oscillating in a shear layer mode regime. It is shown that the use of this splitting procedure largely improves the accuracy of hybrid CAA-simulation with only a minor additional cost.status: publishe