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Hypersonic flow over a flat plate is investigated under a wide range of Mach and Knudsen numbers using both continuum-based approach and DSMC method. The simulated gas is argon thus to isolate the high temperature effects. The Mach number of the flow lies between 5 and 30 whereas the Knudsen number covers the entire flow regime. It is learned that local rarefaction is observed near the leading edge even when the Knudsen number is around 0.001. The continuum breakdown can be identified using a nonequilibrium parameter that evaluates the difference among the temperature components. It is also learned that there is competition between viscous effects and rarefied effects on the skin friction. The total drag on the plate can be well estimated using a bridging formula that connects the results from the continuum and free molecular expressions. In addition, the value of drag depends on the surface temperature. The drag coefficient increases with the surface temperature when the Knudsen number is less than 0.01 but decreases when the Knudsen number is larger than 1.0. [ABSTRACT FROM AUTHOR]

Hypersonic vehicles travel across the atmosphere at very high speed, and the surrounding gas experiences complicated physical and chemical processes. These processes produce real gas effects at high temperature and rarefied gas effects at high altitude where the two effects are coupled through molecular collisions. In this study, we aim to identify the individual real gas and rarefied gas effects by simulating hypersonic flow over a 2D cylinder, a sphere and a blunted cone using a continuum-based CFD approach and the direct simulation Monte Carlo method. It is found that physical processes such as vibrational excitation and chemical reaction will reduce significantly the shock stand-off distance and flow temperature for flows having small Knudsen number. The calculated skin friction and surface heat flux will decrease when the real gas effects are considered in simulations. The trend, however, gets weakened as the Knudsen number increases. It is concluded that the rarefied gas effects weaken the real gas effects on hypersonic flows. [ABSTRACT FROM AUTHOR]

A preliminary hybrid particle-continuum computational framework for simulating hypersonic interacting flows is proposed. The framework consists of the direct simulation Monte Carlo-Information Preservation (DSMC-IP) method coupled with a Navier-Stokes solver. Since the DSMC-IP method provides the macroscopic information in each time step, determination of the continuum fluxes across the interface between the particle and continuum domains becomes straightforward. A hypersonic flow over a two-dimensional wedge is considered as an example and compared with pure particle calculations. The results show that this preliminary hybrid framework is promising but several issues are yet to be resolved. [ABSTRACT FROM AUTHOR]