Adaptive mesh refinement and cut-cell algorithms for DSMC simulation of hypersonic flows.

Abstract

Adaptive mesh refinement (AMR) and cut-cell algorithms were developed for a 3-level Cartesian mesh based Direct Simulation Monte Carlo (DSMC) implementation. The simple and efficient AMR algorithm adapts the cell size to the local mean free path of the flow field. Variable time step technique was implemented together with the AMR algorithm to set a time step consistent with the local mean collision time. The control of simulation particles through the use of variable time step was also illustrated. The cut-cell method decouples the flow field Cartesian mesh and the triangulated surface mesh representing any object inside the flow field. Two key aspects of the cut-cell method: cut-cell sorting and volume calculation were discussed in detail. The 3-level embedded Cartesian mesh combined with AMR and variable time step allows increased flexibility for precise control of local mesh size and time step, both vital for accurate and efficient DSMC simulation. Hypersonic flow simulations were conducted to highlight the performance of AMR, variable time step and cut-cell algorithms. Three dimensional simulation of Planetary probe reproduced the experimental heat flux measurement.