On the Computation of Space-Time Correlations by Large-Eddy Simulation
Abstract
Sound radiated by turbulent flow is dependent on the space-time characteristics of the flow field. According to Lighthill's theory (Lighthill 1952; Proudman 1952), acoustic power spectra in the far-fields are determined by the two-time, two-point Eulerian velocity correlations. This has significant implications to the use of large eddy simulation (LES) for aerodynamic noise prediction. The existing subgrid scale (SGS) models are mostly constructed to predict spatial statistics such as energy spectra (Meneveau & Katz 2000). However, it is not clear whether these models can lead to accurate space-time correlations, or frequency contents at individual wavenumbers. The latter information is essential to accurate noise predictions, because for a given frequency, only the spectral element of the source field corresponding to the acoustic wavenumber in a given direction can radiate in that direction (Crighton 1975). This represents a very small fraction of flow energy, and is very susceptible to numerical and modeling errors. Hence, accurate prediction of the space-time correlation is a new requirement imposed on SGS modeling by aeroacoustic applications. For brevity, we henceforth refer to the two-time, two-point correlation of the velocity field simply as time correlation. It describes the space-time statistics of turbulent flows. The time correlation can be equivalently expressed by a two-time correlation of velocity Fourier modes in spectral space.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2003
- Accession Number
- ADP014814
Entities
People
- Guo-wei He
- Meng Wang
- Sanjiva K. Lele
Organizations
- Chinese Academy of Sciences