Spurious noise in direct noise computation with a finite volume method for automotive applications

The present paper represents a study on spurious noise generated in direct noise computation using finite volume methods. Different sources of spurious noise are examined as well as the mechanism of their generation. This investigation involves two test cases. The first one consists of a turbulence box convected by a uniform flow field. This case serves to identify spurious noise sources and qualitatively evaluate their relevance. The second test case involves a single side mirror mounted on a flat plate, which serves to quantify the level of spurious noise produced and its relevance compared to physical sound generated by the flow past the mirror. Both test cases are calculated using a compressible flow solver for low Mach-number flows utilised with an IDDES approach for turbulence modelling. A new acoustic damping model which damps out acoustic waves without affecting hydrodynamic turbulent fluctuations has been implemented. Furthermore, special emphasis on refinement interfaces is given. Since no measurements are available, the results of the direct noise computation are compared to the results of a method based on Kirchhoff integral.