Introduction

This chapter investigates one-dimensional, compressible, inviscid flow. Flow is said to be one-dimensional when the fluid properties only depend on a single Cartesian coordinate. Flow is said to be compressible when there is a significant variation in the mass density along a given streamline. Generally speaking, compressible flow is much more common in gases than in liquids. As described in Section 1.17, subsonic gas dynamics (i.e., dynamics in which the typical flow speed is much less than the propagation speed of sound waves in the gas) is essentially incompressible, and is governed by the same equations that govern the incompressible flow of liquids. On the other hand, sonic gas dynamics (i.e., dynamics in which the typical flow speed is comparable with the sound speed) exhibits significant differences to subsonic dynamics. Hence, this chapter will concentrate on sonic gas dynamics. More information on this subject can be found in Liepmann & Roshko 1957, Hughes & Brighton 1999, and Milne-Thomson 2011.