Test Particle Monte Carlo Simulation of Return Flux on Various Geometric Surfaces due to Ambient Scatter of Outgassing Molecules

The test particle Monte Carlo (TPMC) method is delineated by taking the molecular return flux problem for the flow past a complete sphere as an example and the return flux on a variety of geometric surfaces, including a complete sphere, a circle flat plate, a convex and concave hemisphere, due to ambient scatter of outgassing molecules is simulated by this method. The return flux ratio (RFR) obtained here for the flow past a sphere is in good agreement with previous results. Then, effects of various outgassing and freestream conditions on RFR for flows past three geometric bodies, including a circle flat plate, a convex and concave hemisphere, have been investigated and compared. Moreover, heuristic arguments about geometric, outgassing and freestream governing parameters provide theoretical references for the evaluation and control of return flux contamination.