Source Formulations and Boundary Treatments for Lighthill’s Analogy Applied to Incompressible Flows

Abstract

Recently, second-order accurate, nonstationary flow simulations became affordable for low-Mach-number industrial applications. This enables the utilization of Lighthill’s acoustic analogy for flow noise prediction. However, many parameters related to the source term computation such as source formulation and truncation, numerical scheme, and boundary treatment influence the results and are explored in this study. An incompressible flow simulation of a simplified heating, ventilation, and air conditioning outlet geometry is set up using a finite volume solver. Aeroacoustic sources are calculated on a finite volume grid. Finally, the sound propagation is computed by means of a finite element solver. If integral source properties related to the boundary treatment and source truncation technique are satisfied, and the ability of the flow simulation to resolve fine scales according to the numerical scheme and grid resolution is taken into account, good agreement with experimental results could be achieved. In summary, the present work demonstrates how Lighthill’s acoustic analogy can be applied to flow results obtained from usual finite volume solvers. Furthermore, these findings are beneficial for result interpretation and error diagnostics of other similar aeroacoustic simulation cases.