114th NIA CFD Seminar: Toward Physically Exact RANS-LES

Topic: Toward Physically Exact RANS-LES
Speaker: Stefan Heinz, NIA Visiting Researcher & Professor of Mathematics, University of Wyoming

Date: Wednesday, May 8, 2019
Time: 10:30am-11:30am
Location: NIA, Room 137

Host:  Ponnampalam Balakumar, NASA/LaRC

Abstract
Accurate and feasible simulations of turbulent flow around aircraft suffer from two major problems. On the one hand, computationally very efficient pure Reynolds-averaged Navier-Stokes (RANS) methods fail to describe the main features of such flows because of their lacking ability to resolve turbulent flows. On the other hand, pure Large Eddy Simulation (LES) methods, which are capable of simulating resolved flow, are computationally way too expensive for wall-bounded turbulent flows. The development of solutions to these problems via the design of hybrid methods involving both RANS and LES elements takes place now over decades. About a thousand research papers following a huge variety of solution strategies are published every year now. The talk describes basic solution strategies in order to highlight conceptual questions. Previous applications of hybrid methods are described then by focusing on hill-type flows involving flow separation. These applications reveal the great potential of hybrid methods to accurately simulate separated flows at computational cost being a fraction of pure LES cost. The applications also reveal significant problems of usually applied methods. The final part of the talk focuses on the solution of some essential problems that were basically unaddressed so far, for example the question of how resolved and modeled turbulent motions can be kept in balance under changing resolution conditions. A theoretical solution to this question is presented for several well-known turbulence models. Initial applications show the potential of these news simulation methods.

Speaker Bio
Dr. Stefan Heinz is Full Professor of Mathematics at the University of Wyoming. Dr. Heinz received his PhD in physics from the Heinrich-Hertz Institute in Berlin, Germany. Prior to joining the University of Wyoming, he held engineering faculty positions at TU Delft, Netherlands, and TU Munich, Germany. He has more than 25 years of research experience in the field of turbulence and turbulent combustion modeling and simulation. Dr. Heinz has published and presented his research through more than 200 international journal articles, conference publications, and invited presentations. He authored two textbooks on turbulence and stochastic processes. He has held visiting professor appointments at several universities and institutes. We won several teaching and research awards, he was honored as Adjunct Professor of Mechanical Engineering at the University of Wyoming. He is a fellow of the Hanse-Wissenschaftskolleg (Institute for Advanced Study, Delmenhorst) in Germany.