In this work we outline a Classical Trajectory Calculation Direct Simulation Monte Carlo (CTC-DSMC) implementation that uses the no-time-counter scheme with a cross-section determined by the interatomic potential energy surface (PES). CTC-DSMC solutions for translational and rotational relaxation in one-dimensional shock waves are compared directly to pure Molecular Dynamics simulations employing an identical PES, where exact agreement is demonstrated for all cases. For the flows considered, long-lived collisions occur within the simulations and their implications for multi-body collisions as well as algorithm implications for the CTC-DSMC method are discussed. A parallelization technique for CTC-DSMC simulations using a heterogeneous multicore CPU/GPU system is demonstrated. Our approach shows good scaling as long as a sufficiently large number of collisions are calculated simultaneously per GPU (~100,000) at each DSMC iteration. We achieve a maximum speedup of 140× on a 4 GPU/CPU system vs. the performance on one CPU core in serial for a diatomic nitrogen shock. The parallelization approach presented here significantly reduces the cost of CTC-DSMC simulations and has the potential to scale to large CPU/GPU clusters, which could enable future application to 3D flows in strong thermochemical nonequilibrium.
Bibliographical noteFunding Information:
This research is supported by Air Force Office of Scientific Research (AFOSR) under Grant No. FA9550-10-1-0075 . The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the AFOSR or the U.S. Government.
Copyright 2019 Elsevier B.V., All rights reserved.
- Direct Simulation Monte Carlo
- Graphical Processing Unit (GPU)
- One dimensional shock
- Rarefied gas dynamics