GALCIT Colloquium

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.