Nonequilibrium Gas Flows
Chapter 10wasdevoted to thephysicalmodelsofnonequilibriumgases. Inwhat follows,we will study the purely gas dynamic features of relaxing gas flows. Nonequilibrium effects, as well as those of viscosity, manifest themselves usually at small gas densities, say, at H ≥ 50 km for bodies of standard dimensions in the atmospheric flight, the two effects often appearing simultaneously. As the viscous flows will be reviewed in the subsequent chapters, we defer an analysis of such situations until then. We note that methodically the main nonequilibrium gas dynamic effects can be established with reference to the example of the very simple three-parameter gas model of Section 10.3, which involves only one kinetic variable λ, along with two basic variables (the pressure p, the temperature T or the enthalpy h, etc.). In many cases, we will restrict ourselves to this model, using the more exact data on the flows of nonequilibrium multicomponent gas mixtures (usually, the air) for the purpose of illustration.