Wall-Modeled Large-Eddy Simulation of Separated Flows

Speaker: Francois Cadieux, STC/NASA Ames Research Center
January 31, 2017

Presentation

Abstract

Many flows of interest for engineering applications are unsteady and display regions of separated or recirculating flow. Turbulence-resolving approaches like direct numerical simulation (DNS) and wall-resolving large eddy simulation (LES) are able to accurately recover the important dynamics of the flow measured in experiments. However, DNS and wall-resolved LES are limited to moderate Reynolds number flows due to the strong requirement of resolving the viscous sub-layer. The newly proposed integral wall model for LES (iWMLES) significantly relaxes this requirement and aims to bring the cost of performing simulations of unsteady, separated flows at high Reynolds number within reach. The model has been validated for developing turbulent boundary layer flows and turbulent flow over an array of cubes. In this work, iWMLES predictions are compared to DNS data for a separating and reattaching fully turbulent boundary layer flow. And to gain insight into the effects of near-wall modeling, a one-to-one comparison to a wall-resolved LES is also attempted.

Biography

Francois Cadieux is a research scientist in the Computational Aerosciences Branch of the NASA Advanced Supercomputing Division at NASA Ames Research Center. Before joining the launch ascent and vehicle aerodynamics (LAVA) group in September 2016, Cadieux was a postdoctoral fellow at the Flow Physics and Computation Lab under the supervision of Prof. Rajat Mittal at Johns Hopkins University. His research focused on developing higher-fidelity computational fluid dynamics simulation tools that are fast enough to inform the design of engineering applications, like wall-modeled large-eddy simulation. Cadieux also investigated the dynamics of active flow control to mitigate flow separation and delay stall. During his graduate work with Prof. Julian A. Domaradzki, Cadieux probed the limits of under-resolved large-eddy simulation (LES) for separated flows applicable to small unmanned aerial vehicles and low pressure turbines, and quantified the importance of numerical dissipation effects when performing LES on such coarse grids. He obtained his Ph.D. in aerospace engineering from the University of Southern California in 2015.

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