Assessment of Gas-Surface Interaction Models for Computation of RarefiedHypersonic Flows.

Gas-surface Interactions;Computation;Rarefied;Hypersonic;Spaceflight;Aerospace Engineering;Engineering;Aerospace Engineering

Padilla, Jose FernandoRoe, Philip L. ;

University of Michigan

关键词: Gas-surface Interactions;    Computation;    Rarefied;    Hypersonic;    Spaceflight;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/58489/padillaj_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Over the next few decades, spaceflight is expected to become more common through the resurgence of manned space exploration and the rise of commercial manned spaceflight. An essential role for the efficient research and development of suborbital spaceflight is played by computational simulation of rarefied hypersonic flows. Among the few classes of computational approaches for examining rarefied gas dynamics, the most widely used approach, for spatial scales relevant to suborbital spaceflight, is the direct simulation Monte Carlo (DSMC) method. Although the DSMC method has been under development for over forty years, there are still many areas where improvements can be made. One particular area is the associated numerical modeling of interactions between gas molecules and solid surfaces. Gas-surface interactions are not well understood for rarefied hypersonic conditions, although various models have been developed. This thesis ultimately focuses on assessing two common gas-surface interaction models in use with the DSMC method, the Maxwell model and the Cercignani, Lampis and Lord (CLL) model.In the search for a definitive thesis goal and as a consequence of the analysis tools developed for achieving the definitive thesis goal, several aspects of DSMC analysis are examined. Initially, procedures to determine aerodynamic coefficients from DSMC simulations are validated against certain windtunnel test data and an independent DSMC code. Then, sensitivity studies are performed involving aerothermodynamics predictions for the Apollo 6, at the 110 km altitude return trajectory point. This reveals the significance of gas-surface surface interaction models in rarefied hypersonic flows. A review of existing gas-surface interaction models motivates the assessment of the Maxwell and CLL models. The two models are scrutinized with the help of relatively recent windtunnel test measurements and procedures to extract surface scattering distributions. Both models yield similar results; however, the CLL model is physically more realistic, while having similar computational expense. The procedures to extract molecular velocity statistics and distribution shapes from DSMC simulations enable a detailed perspective on the extent of thermal nonequilibrium in the flow field. Finally, Apollo 6 flight simulations using the Maxwell and CLL models demonstrate the sensitivity of rarefied aerothermodynamic analysis to the gas-surface interaction model.