ABSTRACT
This chapter discusses the flow of gases in which changes of pressure and velocity are associated with significant changes of density. The density of a gas is related to both the pressure and the temperature all changes of density involve thermodynamic effects. Certain combinations of fluid properties occur so frequently in thermodynamic problems that they may usefully be given symbols of their own. Compressibility effects of great importance arise when an aircraft flies at or near the speed of sound. The chapter considers an aerofoil such as a thin wing of large span and a section where the flow is uninfluenced by fuselage, wing-tips or engine nacelles. In several respects the flow of gases is similar to the flow of liquids in open channels. This is because similar equations of energy, momentum and continuity apply to the certain types of flow.
