Application of LES combined with a wave equation for the simulation of noise induced by a flow past a generic side mirror

Abstract

The paper presents validation results of a hybrid simulation method for aeroacoustics in turbulent flows at low Mach numbers. The hybrid method implemented in the Ansys Fluent® CFD package applies a scale-resolving turbulence model to compute the noise sources in an incompressible flow, while the noise propagation is modeled by a wave equation formulated for the acoustic potential. The selected test case deals with a flow and a sound field around a generic side view mirror of a car. The SBES model by Menter, which belongs to the class of the RANS-LES models, is used for the flow simulation. It switches to the Large Eddy Simulation (LES) mode in separated mixing layers and recirculation zone behind the mirror as well as in the following wake, where flow develops intensive turbulence and dominating noise sources. The acoustics wave equation is formulated in the model form of Kaltenbacher et al. and is applied in the time domain. The overall calculation is performed as a transient co-simulation on the same mesh using the finite-volume discretization method for both the flow and the acoustics parts. The wave equation is advanced in time using the HHT-α method. Obtained distribution of the mean wall pressure over the mirror surface closely matches the experimental one. Rich content of the resolved turbulent vortices in the separation zone and good agreement of the calculated and measured wall pressure spectra at sensor locations downstream the mirror evidence a proper LES resolution quality of noise sources. Comparison of the computed noise spectra at the remote microphones with the experimental data demonstrates the sound propagation accuracy and validates the overall aeroacoustics simulation method.

A FEM Flow Impact Acoustic Model Applied to Rapid Computation of Ocean-Acoustic Remote Sensing in Mesoscale Eddy Seas

“…The model-solving process describes the acoustic field in the form of time harmonics on the basis of the 3D convective fluctuation equations, which transform the convective fluctuation equations in the time domain into the convective Helmholtz equations in the frequency domain [26], improving the computational speed. Meanwhile, under the premise that the sound source is a small-amplitude wave, the linear Euler equations are obtained by neglecting the nonlinear effects in the convective Helmholtz equations [27], and the fluid flow brought about by the mesoscale vortices is reduced to a nonviscous, non-rotating velocity potential by referring to the simplifications in aerodynamic acoustics [28][29][30].…”