Frozen gas model

The name "frozen gas" may be deceptive. A frozen gas isn't "frozen" like ice is frozen water. Rather a frozen gas is "frozen" in time (all chemical reactions area unit assumed to own stopped). Chemical reactions area unit usually driven by collisions between molecules. If force per unit area is slowly reduced specified chemical reactions will continue then the gas will stay in equilibrium. However, it's attainable for force per unit area to be therefore suddenly reduced that nearly all chemical reactions stop. For that state of affairs the gas is taken into account frozen.

The distinction between equilibrium and frozen is very important as a result of it's attainable for a gas like air to own considerably totally different properties (speed-of-sound, consistency etc.) for a similar physical science state; e.g., pressure and temperature. Frozen gas may be a major issue within the wake behind associate degree entry vehicle. throughout return, free stream air is compressed to warmth and pressure by the entry vehicle's blast wave. Non-equilibrium air within the shock layer is then transported past the entry vehicle's leading aspect into a section of quickly increasing flow that causes physical change. The frozen air will then be entrained into a trailing vortex behind the entry vehicle. properly modelling the flow within the wake of associate degree entry vehicle is incredibly troublesome. Thermal protection protect (TPS) heating within the vehicle's afterbody is typically not terribly high, however the pure mathematics and unsteadiness of the vehicle's wake will considerably influence mechanics (pitching moment) and significantly dynamic stability.