Gas Dynamic Model and Equations of Gas Flows
In this chapter we will formulate a gas flow model that will be termed gas dynamic; it is adequate to the typical regimes of themotion of vehicles of standard dimensions inmoderately dense gasmedia, such as the atmospheres of Earth and some other planets, or the flow past the models of such vehicles in bench testing. Within the framework of this model, the equations governing the gas flowswill be derived and some attendant theoretical problems will be elucidated. The basic mechanical and physical laws governing gas dynamic processes are first for-
mulatedwith reference to the simple example of the one-dimensional flow, which does not require, in particular, making recourse to complicated vector and tensor procedures; we next pass on to the derivation of the gas dynamic equations in the general form. At the same time, some classical elements of the theory, such as kinematics, tensor anal-
ysis, and so on, are given only in a condensed form. Their detailed presentation can be found in the books by Kochin, Kibel, and Roze (1963), Loitsyanskii (1966), Rakhmatullin et al. (1970), Sedov (1972), Landau and Lifshitz (1959), and others.