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Adjoint Sensitivity Analysis for Scale-Resolving Turbulent Flow Solvers

Event Type: 
Date and Time: 
Friday, March 24, 2017 - 16:15
Location: 
CTR Conference Room 103
Event Sponsor: 
Parviz Moin, Director of Center for Turbulence Research
Speaker(s): 
Dr. Patrick Joseph Blonigan, Postdoctoral Fellow, NASA Ames Research Center

Adjoint-based sensitivity methods are powerful design tools for engineers who use computational fluid dynamics. In recent years, these engineers have started to use scale-resolving simulations like large-eddy simulations (LES) and direct numerical simulations (DNS), which resolve more scales in complex flows with unsteady separation and jets than Reynolds-averaged Navier-Stokes (RANS) methods. However, the conventional adjoint method computes large, unusable sensitivities for scale-resolving simulations, which unlike RANS simulations exhibit the chaotic dynamics inherent in turbulent flows. Sensitivity analysis based on least-squares shadowing (LSS) avoids the issues encountered by conventional adjoint methods, but has a high computational cost even for relatively small simulations. The following talk discusses a new, more computationally efficient formulation of LSS and its application to turbulent flows simulated with Eddy, a discontinuous-Galkerin spectral-element-method LES/DNS solver. First, the new LSS formulation, called “non-intrusive” LSS, is outlined, followed by a cost analysis of the method. Results are presented for the minimal flow unit, a turbulent channel flow with a limited streamwise and spanwise domain.

Bio: 
Dr. Blonigan received his B.S. in Mechanical Engineering from Cornell University in 2011. In June 2011 he started his Ph.D. at Massachusetts Institute of Technology in the Department of Aeronautics and Astronautics, and he worked with Professor Qiqi Wang, developing new approaches for sensitivity analysis of chaotic dynamical systems and fluid flow simulations. Dr. Blonigan received his M.S. in 2013 and his Ph.D. in 2016, and he is now a Postdoctoral Fellow at NASA Ames Research Center where he is applying his Ph.D. research on chaotic sensitivity analysis to scale-resolving turbulent flow solvers.