Implementation and Comparison of Slip-flow Boundary Conditions for Perfect Gas Hypersonic Flow Simulations

Abstract

Upon re-entry into the earth’s atmosphere, a hypersonic vehicle experiences a continuous increase in the density of the surrounding fluid. Coming from a highly rarefied atmosphere, the vehicle passes various flow regimes. At high altitudes, molecular collisions with the vehicle’s surface dominate the airflow around the vehicle. This regime is known as the free molecular regime. While approaching the earth’s surface, the atmosphere will get progressively denser until the vehicle reaches the continuum regime, in which the surrounding gas is no longer considered as individual molecules but as a continuum. In between these two regimes, the vehicle passes the transition and slip regime, where slip effects at the surface, such as velocity slip and temperature jump, become relevant. For the design and construction of hypersonic vehicles and re-entry configurations, it is essential to accurately predict the aerodynamic forces and the heat transfer throughout all of those flow regimes. Rarefaction effects impact the design of the thermal protection system and compromise the aerodynamic efficiency of the vehicle.