Enhancements of the Parallelized Dsmc-Mlg Method for Applications to Complex Hypersonic Transitional-Regime Flows.
Previous applications of the combined Direct Simulation Monte Carlo (DSMC) and Monotonic Lagrangian Grid (MLG) methodology have been limited to simple rectangular geometries. Real flow problems in many areas of physics and engineering often involve complex geometries. This dissertation describes the application of the combined DSMC-MLG method to a more complex flowfield. The flow conditions being studied belong to the transitional flow regime of fluid dynamics. Direct Simulation Monte Carlo is a molecular approach that has been used widely and with great success in predicting transitional regime flows. The MLG technique combined with DSMC allows automatic grid adaptation based on the local number densities. The DSMC-MLG code, recently optimized on the CM-5E parallel supercomputer, has proven to be fast and efficient. The improvement in the computing speed has made it possible to apply the DSMC-MLG technique to more complex flowfields. The present work is the first to successfully simulate a high-speed, high Kn flow through a channel with a wedge using DSMC-MLG. The channel-wedge geometry creates a complex flowfield with a wide range of fundamental aerodynamic phenomena, such as oblique shocks, rarefraction waves, boundary layers, boundary layer separation, recirculating region, and their mutual interactions. The calculations also show low-density effects such as the slip in velocity and temperature of the gas adjacent to the solid surfaces. A method was developed to obtain a geometry-conforming MLG and was successfully demonstrated for the channel-wedge system. Furthermore, the method of Stochastic Grid Restructuring (SGR) is included in the current code to find a high-quality MLG for the channel-wedge calculations. The results obtained with a high-quality MLG indicates sharper and more resolved flowfield features than those obtained with a poor-quality MLG. The implementation of a new inflow-outflow boundary condition to the code resulted in accurate control of the geometric length of the channel. Pressure calculations using molecular momentum transfer show that the perfect gas equation of state is applicable at low-density conditions.
- Pub Date:
- January 1995
- Engineering: Aerospace; Physics: Molecular