Development and Implementation of Practical Optimal LES Models
ILLINOIS UNIV AT URBANA DEPT OF THEORETICAL AND APPLIED MECHANICS
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One of the most promising techniques for the prediction of turbulent flows is that of Large Eddy Simulation LES, in which an under-resolved representation of the turbulence is simulated numerically by modeling the effects of the unresolved small-scales on the simulation. Such simulations have been applied in several flows with reasonable success. However, there are several outstanding problems that need to be addressed before LES can fulfill its promise as a tool for turbulence prediction in engineering flows. The most serious problems limiting the usefulness of LES is the representation of turbulence near walls and other strong inhomogeneities and the dependence of models on the filter andor numerical discretization. The optimal LES formulation provides a rigorous framework in which to address these issues and to develop and analyze LES models and simulations. Optimal LES modeling has been found to produce accurate LES simulations when based on reliable statistical information, so the primary thrust of the current research is to reduce or eliminate the need for empirical statistical input through theory and modeling of turbulence statistics. When small-scale isotropy is a valid assumption, the Kolmogorov theory and isotropy can provide much information. However, when inhomogeneity and anisotropy are strong, or the Reynolds number is not too large, more information will be required, and models for this are being developed, particularly for near-wall turbulence. Theoretical models for the turbulence multi-point correlations allow optimal LES models to be implemented relatively simply in production CFD codes, and preliminary implementations in FDL3DI at AFRL have been pursued.
- Numerical Mathematics
- Fluid Mechanics