Investigation on a coupled Navier-Stokes-Direct Simulation Monte Carlo method for the simulation of plume flowfield of a conical nozzle

To assess the plume effects of space thrusters, the accurate plume flowfield is indispensable. The plume flow of thrusters involves both continuum and rarefied flow regimes. Coupled Navier-Stokes-Direct Simulation Monte Carlo (NS-DSMC) method is a major approach to the simulation of continuum-rarefied flows. An axisymmetric coupled NS-DSMC solver, possessing adaptive-interface and two-way coupling features, is investigated in this paper for the simulation of the nozzle and plume flows of thrusters. The state-based coupling scheme is adopted, and the gradient local Knudsen number is used to indicate the breakdown of continuum solver. The nitrogen flows in a conical nozzle and its plume are chosen as the reference case to test the coupled solver. The threshold value of the continuum breakdown parameter is studied based on both theoretical kinetic velocity sampling and coupled numerical tests. Succeeding comparisons between coupled and full DSMC results demonstrate their conformities, meanwhile, the former saves 58.8% computational time. The pitot pressure evaluated from the coupled simulation result is compared with the experimental data proposed in literatures, revealing that the coupled method makes precise predictions on the experimental pitot pressure. Copyright (C) 2014 John Wiley & Sons, Ltd.