04-24-2019 | Johan Larsson: Grid-Adaptation for Large Eddy Simulations

112th NIA CFD Seminar: Grid-Adaptation for Large Eddy Simulations 

NOTE: Location has moved to Room 137.

Date: Wednesday, April 24, 2019
Time: 11am-noon (EDT)
Room: NIA, Room 137

Speaker: Johan Larsson, Associate Professor, University of Maryland

Link: http://nia-mediasite.nianet.org/NIAMediasite100/Catalog/Full/c40f721b665a4091b7d8bcb6a128fdbd21

Abstract: While grid-adaptation has reached a certain level of maturity in several areas of CFD, the application to turbulence-resolving simulations (most notably, LES) is still in its infancy. The chaotic and broadband nature of the dynamics in an LES leads to 2 major challenges. First, the grid affects both the numerical and modeling error in LES, compared to only the numerical error in non-broadband problems. As a result, the estimation of the local error production cannot be purely mathematical but must also require physics-informed reasoning and assumptions. Secondly, the chaotic nature causes adjoints to diverge exponentially, which makes direct application of the adjoint-weighted residual method cumbersome. The talk will discuss 3 separate approaches to this problem that have been developed in the PI’s group over the last couple of years, with applications to turbulent channel flow and the flow over a backward-facing step. Outstanding issues and ongoing/future work will be discussed, with some emphasis on the ongoing/planned work under the current NRA-funded project to merge wall-modeled LES with algorithms for grid-adaptation and adaptively finding the optimal thickness of the wall-modeled layer.

Speaker Bio: Johan Larsson is an Associate Professor at the University of Maryland where he works on multiple problems in the field of computational turbulence including wall-modeling for large eddy simulation, grid-adaptation for turbulence-resolving simulations, high-speed turbulent flows, and uncertainty quantification for turbulence problems. He earned his PhD at the University of Waterloo, Canada, in 2006, and then worked at the Center for Turbulence Research at Stanford University as a postdoctoral fellow and Research Associate for 6 years before joining the University of Maryland in 2012.