MAE 298 SEMINAR: What’s So Hard about Modeling Turbulence Using Large Eddy Simulation?

Abstract: One of the greatest challenges to making reliable predictions of complex high-Reynolds-number fluid flows is accounting for the effects of turbulence. In engineering applications, turbulence is almost always represented using Reynolds-averaged Navier-Stokes (RANS) models, but such models are widely acknowledged to be unreliable in complex flows. Large eddy simulation (LES) of turbulence, in which the largest scales of turbulence are simulated while the effects of the smaller unresolved scales are modeled, is expected to to be a more accurate and robust modeling approach. And, provided sufficient resolution is used, LES can indeed be very reliable. However, for LES to be a practical tool for engineering applications, it is important that it provide reliable model predictions with the coarsest possible resolution. Such coarse resolution in LES introduces a number of complications that are generally insignificant when much finer resolution is used. Among these complications are the effects of: numerical discretization, inhomogeneous and anisotropic resolution, filtering, and model inconsistencies. We will discuss the effects of these complications, as well as analytical and modeling strategies to help overcome them and improve the reliability of coarsely resolved LES. 

Bio: Robert D. Moser holds the W. A. “Tex” Moncrief Jr. Chair in Computational Engineering and Sciences and is professor in the Walker Department of Mechanical Engineering. He serves as the director of the Oden Institute’s Center for Predictive Engineering and Computational Sciences (PECOS) and deputy director of the Oden Institute. Moser earned his Ph.D. in mechanical engineering from Stanford University. Before coming to The University of Texas at Austin, he was a research scientist at the NASA-Ames Research Center and then a professor of theoretical and applied mechanics at the University of Illinois. Moser conducts research on the modeling and numerical simulation of turbulence and other complex fluid flow phenomena. He has been a leader in the use of direct numerical simulation for investigating and modeling turbulent flows, and the application of such direct simulations to the development of large eddy simulation models. He has also been active in the development of highly accurate high-resolution numerical approximations for use in simulation of turbulence and other complex flows. Finally, Moser has been working to develop new approaches for the validation of computational models and to assess their reliability. Moser is a fellow of the American Physical Society, and was awarded the NASA Medal for Exceptional Scientific Achievement.