Direct molecular simulation: How DSMC has improved CFD for hypersonics
Professor Tom Schwartzentruber Department of Aerospace Engineering and Mechanics University of Minnesota, Minneapolis, MN, USA
Predicting what happens as a hypersonic vehicle flies through the atmosphere involves a lot of interesting physics. The strong shock wave, generated ahead of the vehicle, superheats the air to thousands of degrees and partially dissociates the air into atomic oxygen and nitrogen. The vehicle heat shield must simultaneously withstand high temperatures and intense surface chemistry driven by these reactive atomic species. Predicting such effects requires understanding the interplay between fluid dynamics, thermodynamics, and chemical kinetics; a research field referred to as aerothermodynamics. We have reached the point where this thin shock layer can be studied at the scale of individual molecular collisions. Direct molecular simulation (DMS) can now be performed where the only model input consists of the forces between atoms as dictated entirely by quantum chemistry. The direct simulation Monte Carlo (DSMC) method lies at the heart of the DMS method and has enabled significant insight into aerothermodynamics for hypersonic flows. In this presentation the DMS method will be described and results for internal energy relaxation, chemical kinetics, and multi-component diffusion will be highlighted. Finally, new models for computational fluid dynamics (CFD) will be described along with verification against DMS and DSMC, as well as initial validation against hypersonic experimental measurements using advanced laser diagnostic techniques.
Bio: Tom Schwartzentruber received his Bachelor’s degree in engineering science and his Master’s degree in aerospace engineering from the University of Toronto. He then received his doctorate degree in aerospace engineering from the University of Michigan. For his doctorate work he received the AIAA Orville and Wilbur Wright graduate award. He joined the faculty in the Aerospace Engineering and Mechanics department at the University of Minnesota in 2008, after which he received a Young Investigator Program Award from the AFOSR and the University of Minnesota Taylor Career Development Award for exceptional contributions by a candidate for tenure. He specializes in particle simulation methods such as direct simulation Monte Carlo (DSMC) and molecular dynamics (MD), including coupling such methods with each other and with continuum computational fluid dynamics (CFD) methods. Currently, his research group is involved in a number of projects spanning hypersonic nonequilibrium reacting flows, gas-surface interactions and ablation, hybrid particle-continuum methods, satellite material effects in low earth orbit.