Aeroacoustic sources in turbulent flow through a pipe with a sharp orifice predicted by Large-Eddy Simulation

The method of Large-Eddy Simulation (LES) has in-
creasingly gained popularity, as it resolves a significant
part of the vortical motion directly 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 Computa-
tional Aero-acoustics (CAA). The possible sound emis-
sion generated by turbulent vortical motion is of grow-
ing 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 of the
vehicle may lead to unfavorable flow conditions. The
present study performs incompressible LES to predict the
turbulent flow field of an orifice inside a straight circular
pipe. The predicted instantaneous flow field is used to
evaluate aeroacoustic source terms for different acoustic
equations, such as Lighthill’s wave equation or the Per-
turbed Convective Wave Equation (PCWE). The con-
tribution of the unresolved scales, which is supplied to
the acoustic sources by the employed SGS-model, is spe-
cially investigated. The computational results are also
compared against experimental data from reliable mea-
surements.