ABSTRACT
It has been found experimentally that, under some circumstances, it is possible for an almost spontaneous change to occur in a flow, with the velocity decreasing and the pressure increasing through this region of sharp change. The possibility that such a change can actually occur follows from the analysis given below. It has been found experimentally, and it also follows from the analysis given below, that such regions of sharp change can only occur if the initial flow is supersonic. The extremely thin region in which the transition from the initial supersonic velocity, relatively low-pressure state to the state that involves a relatively low velocity and high pressure is termed a shock wave. The changes that occur through a normal shock wave, i.e., a shock wave that is straight and at right angles to the flow direction, are shown in Figure 5.1. A photograph of a normal shock wave is shown in Figure 5.2.
