ABSTRACT

Chapter 1 contains a discussion of some of the assumptions that are commonly adopted in the analysis of compressible gas flows, i.e., of the assumptions that are commonly used in modeling such flows. It was explained in Chapter 1 that most such analyses are based on the assumptions that

• The specific heats of the gas are constant • The perfect gas law, p/ρ = RT, applies • There are no changes in the physical nature of the gas in the flow • The gas is in thermodynamic equilibrium

However, as discussed in the previous chapter, if the temperature in the flow becomes very high, it is possible that some of these assumptions will cease to be valid. To investigate again (a discussion of this was also given in the previous chapter) whether it is possible to get such high temperatures in a flow, consider the flow of air through a normal shock wave. The air will be assumed to have a temperature of 216.7 K (i.e., –56.3°C) ahead of the shock. This is the temperature in the so-called standard atmosphere between an altitude of ~11,000 and ~25,000 m. The situation considered is therefore as shown in Figure 12.1a.