University of Minnesota
Aerospace Engineering and Mechanics
Spring 2001 Seminar Series



A Radical Approach to Large Eddy Simulation of Turbulence


Prof. Robert Moser

Department of Theoretical and Applied Mechanics, University of Illinois at Urbana-Champaign


Abstract


Large eddy simulation (LES is a very promising technique for the prediction of turbulent fluid flows. However, there remains in LES, the problem of modeling the unsimulated small scales. In this talk, LES subgrid modeling is approached as a formal optimization problem. A rigorous result shows that the best-possible deterministic subgrid model has several good features, particularly it guarantees that the single-time statistics of the simulated LES will be correct. Unfortunately, this ideal LES model is uncomputable, though it can be approximated. The study of formal approximations to the ideal yield many interesting results regarding the nature of subgrid models and LES. Among these are that in many cases, the exact subgrid term appears to be largely stochastic. Also, in strongly inhomogeneous flows, the subgrid term makes an important contribution to the spatial transport of resolved scale kinetic energy, in addition to dissipation, and this must be represented by the model. Finally, when casting LES in the context of finite volume representations, the resulting optimal LES evolution schemes look neither like standard finite volume representations or like representation of common LES models.

Friday, February 23, 2001
209 Akerman Hall
2:30-3:30 p.m.


**Refreshments served after the seminar in 107 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior Secretary, 625-8000.