Simulation of High-Altitude Plume Flow Fields Using a Hybrid Continuum CFD/DSMC Approach

Abstract

Rarefied flow conditions can have an impact on performance and radiation characterization at not only high-altitudes conditions but also for separated flow regions either behind blunt bodies or around divert jets at high continuum altitudes. Under rarefied flow conditions, standard continuum CFD methodologies fall short. More appropriate are Direct Simulation Monte Carlo (DSMC) techniques. However, DSMC techniques can quickly become intractable for flows that are either primarily rarefied and have small continuum regions, or, that are primarily continuum with regions of rarefied flow. The solution is to partition the flow into continuum and non-continuum regimes separated by an interface surface. Unfortunately, the interface surface can be quite complex leading to a substantial amount of ‘man-in-the-loop’ effort to obtain a surface that is both well-posed and compatible with the DSMC solver. An automated Arbitrary Breakdown Surface Generation procedure is developed to address this situation. This automated procedure not only reduces the amount of ‘man-in-the-loop’ effort but is also general enough to apply to a wide variety of continuum/non-continuum coupling problems. Particulates (from solid motors) are also of interest for high-altitude plume flowfields. Past efforts to simulate particles within the rarefied regime have decoupled the particulate simulation from the rarefied gas simulation. This inefficient process is eliminated by implementing particle integration directly into the DAC97 DSMC solver. Some generic straightback plume flow field simulations and divert jet studies serve to demonstrate the capabilities of these new procedures.