Enabling general meso-scale ablation simulations via direct simulation Monte Carlo

Direct simulation Monte Carlo (DSMC) [1] is a stochastic particle method that can track individual gas-surface and gas-gas reactions, making it a prime candidate for simulating ablation at meso-scales. Recently, we have developed a surface conversion capability within Sandia’s direct simulation Monte Carlo solver, SPARTA [2] to allow DSMC ablation simulations of complex bodies. However, for the surface conversion to be robust, the vertices of the surface elements shift. Moreover, the simulated surface recession does not correctly match the expected local mass flux. The combination of these two causes DSMC to augment the surface roughness which can mask cell-level features (which are on the scale of the mean free path) and disturb the nearby flow. Two modifications are made to the ablation framework: inner indices and multi-point cell decrement. The combination of the two enable more physically realistic DSMC ablation simulations.

[1] Bird, G. A. (1994). Molecular gas dynamics and the direct simulation of gas flows. Oxford university press.

[2] Plimpton, S. J., Moore, S. G., Borner, A., Stagg, A. K., Koehler, T. P., Torczynski, J. R., & Gallis, M. A. (2019). Direct simulation Monte Carlo on petaflop supercomputers and beyond. Physics of Fluids, 31(8).