Velocity Slip and Temperature Jump in Hypersonic Aerothermodynamics

Abstract

Hypersonic vehicles experience different flow regimes during flight due to changes in atmospheric density. Computational fluid dynamics, although relatively computationally inexpensive, is not physically accurate in areas of highly nonequilibrium flows. The direct simulation Monte Carlo method, although physically accurate for all flow regimes, is relatively computationally expensive. In a continuing effort to understand the performance of computational fluid dynamics and direct simulation Monte Carlo in hypersonic flows, the current study investigates the effect of continuum breakdown on surface aerothermodynamic properties (pressure, shear stress, and heat transfer rate) of a cylinder in Mach-10 and Mach-25 flows of argon gas for several different flow regimes, from the continuum to a rarefied gas. Several different velocity-slip and temperature-jump boundary conditions are examined for use with the computational fluid dynamics method. Computational fluid dynamics and direct simulation Monte Carlo solutions are obtained at each condition. Total drag and peak heat transfer rate predictions by computational fluid dynamics remain within about 6% of the direct simulation Monte Carlo predictions for all regimes considered, with the Gokcen-type slip condition giving the best results.