Two-phase coupled model for DSMC plume simulation

To numerically simulate two-phase plume field with gas molecules and particles, self-developed Plume Work Station (PWS) based on Direct Simulation Monte Carlo (DSMC) method was used to evaluate two-phase coupled models. Particles introduced to a uniform gas stream were computed. The obtained DSMC solution is in agreement with the analytic solution, proving that the gas-particle one-way coupled model is reasonable. The gas-surface reflection was computed by an indirect manner. Firstly the global coordinate system was transformed to local particle system, and the normal direction was determined. Then the specular reflection or diffuse reflection was conducted in the normal coordinate system. Another way was to use known distribution functions of reflection vectors directly. 1 × 10⁶ numerical tests were conducted for the same gas-surface reflection using both approaches. Results of specular reflection satisfy the spatial uniform distribution, and results of diffuse reflection match well. Two-phase flow field of 150N liquid rocket engine was also simulated in two ways. Gas fields given by two methods are almost the same. The computation efficiency of indirect method is a little higher. The liquid droplets affect the plume field only near the axis line of the engine. The plume temperature and pressure increase and Mach number decreases by comparing to the computational results without droplets.