Multi-scale modeling of complex flows at extreme computational scales
Dr. Spencer Bryngelson
Computational Science and Engineering, Georgia Tech
Wednesday, September 6, 2023
MRDC Building, Room 4211
Many fluid flows display at a wide range of space and time scales. Turbulent and multiphase flows can include small eddies or particles, but likewise large advected features. This challenge makes some degree of multi-scale modeling or homogenization necessary. Such models are restricted, though: they should be numerically accurate, physically consistent, computationally expedient, and more. I present two tools crafted for this purpose. First, the fast macroscopic forcing method (Fast MFM), which is based on an elliptic pruning procedure that localizes solution operators and sparse matrix-vector sampling. We recover eddy-diffusivity operators with a convergence that beats the best spectral approximation (from the SVD), attenuating the cost of, for example, targeted RANS closures. I also present a moment-based method for closing multiphase flow equations. Buttressed by a recurrent neural network, it is numerically stable and achieves state-of-the-art accuracy. I close with a discussion of conducting these simulations near exascale. Our simulations scale ideally on the entirety of ORNL Summit's GPUs, though the HPC landscape continues to shift.
Spencer Bryngelson joined Georgia Tech in 2021 as a tenure-track assistant professor in the College of Computing. Previously, he was a senior postdoctoral researcher at Caltech (with Tim Colonius). He has been a visiting researcher at MIT (with Themis Sapsis) and a postdoctoral researcher at the Center for Exascale Simulation of Plasma-Coupled Combustion (with Dan Bodony). He received his Ph.D. and M.S. in Theoretical and Applied Mechanics from the University of Illinois at Urbana-Champaign in 2017 and 2015, working with Jonathan Freund. In 2013, he received B.S. degrees in both Mechanical Engineering and Mathematics from the University of Michigan-Dearborn. Spencer won a young investigator award from Oak Ridge National Lab, the UIUC Outstanding Dissertation Award, and the Hassan Aref Award for research in fluid dynamics.