Aeroacoustic sources in turbulent flow through a 90° pipe bend predicted by Large-Eddy Simulation

The method of Large-Eddy Simulation (LES) has increasingly gained popularity, as it directly captures a major part of the unsteady vortical motion in a turbulent flow field. The uncertainty of turbulence modeling is thus limited to the unresolved sub-grid scales (SGS). This makes LES a highly attractive method for predicting flow-induced sound sources for use in hybrid Computational Aeroacoustics (CAA). The possible sound emission generated by turbulent motion is of growing importance in the design of flow-guiding components. This is especially the case in electric vehicles, where the masking noise of the combustion engine is absent and limited space in the vehicle’s engine compartment may lead to unfavorable flow conditions.The present study performs incompressible LES to predict the turbulent flow field of a 90° circular pipe bend. The computational results are compared against experimental data from dedicated measurements and existing numerical solutions in literature. The predicted instantaneous flow field is used to evaluate acoustic source terms for different acoustic formulations, such as Lighthill’s acoustic analogy and the Perturbed Convective Wave Equation (PCWE). A special focus is on the sound generation in the separated flow region at the exit of the bend.