In Chapter 6 we investigated sound wave propagation in a compressible fluid (air) under the hypothesis that sound waves are considered to be due to small amplitude oscillatory motion of the medium. Therefore Chapter 6, which was devoted to sound waves in air, involved a linearized theory whereby the linear wave equation was invoked. In this chapter we shall extend the theory of wave propagation in a compressible fluid to a more general treatment, in which we shall take into account large amplitude wave propagation of supersonic flow (which involves nonlinear phenomena), and shock waves (which involve discontinuities in some of the dynamic and thermodynamic variables). We shall show, for example, that the wave front for a sound wave is the limiting case of the shock front for supersonic flow where the shock strength becomes infinitely weak and the flow field becomes linearized. It also appears that, for subsonic flow, there can be no wave propagation because of the different character of the partial differential equations (PDEs) that govern the flow. Transonic flow involves a transition between subsonic and supersonic flow. Steady flows in which this transition occurs are called mixed or transonic flows, and the surface where the transition occurs is called the transitional or sonic surface.
KeywordsEntropy Vortex Mercury Enthalpy Attenuation
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