A kinematic subgrid scale model for large-eddy simulation of turbulence-generated sound

Abstract

In the hybrid approach of large-eddy simulation (LES) and Lighthill's acoustic analogy for turbulence-generated sound, the turbulence source fields are obtained using an LES and the turbulence-generated sound at far fields is calculated from Lighthill's acoustic analogy. As only the velocity fields at resolved scales are available from the LES, the Lighthill stress tensor, serving as a source term in Lighthill's acoustic equation, has to be evaluated from the resolved velocity fields. As a result, the contribution from the unresolved velocity fields is missing in the conventional LES. The sound of missing scales is shown to be important and hence needs to be modeled. The present study proposes a kinematic subgrid-scale (SGS) model which recasts the unresolved velocity fields into Lighthill's stress tensors. A kinematic simulation is used to construct the unresolved velocity fields with the imposed temporal statistics, which is consistent with the random sweeping hypothesis. The kinematic SGS model is used to calculate sound power spectra from isotropic turbulence and yields an improved result: the missing portion of the sound power spectra is approximately recovered in the LES.

Keywords:

• large-eddy simulation
• turbulence-generated sound
• kinematic simulation

Acknowledgements

This work was supported by the Chinese Academy of Sciences under the Innovative Project “Multi-scale modeling and simulation in complex systems” (KJCX-SW-L08), National Basic Research Program of China (973 Program) under Project No. 2007CB814800 and National Natural Science Foundation of China under Project Nos. 10325211, 10628206 and 10732090.