CHAPTER 6 - Plane Irrotational Flow of an Ideal Gas

Abstract

This chapter discusses the plane irrotational flow of an ideal gas. The chapter discusses subsonic flow and supersonic flow past a thin aerofoil. The Mach number of the flow in a supersonic wind tunnel can be determined by introducing a fine needle or probe into the stream and measuring the inclination of the Mach waves relative to the direction of the undisturbed flow. The Mach waves can be made visible by virtue of the fact that they involve changes of density and, therefore, of the refractive index of the gas. In the case of a subsonic stream, just as in the flow of an incompressible fluid, the pressure perturbation at any point of the flow depends on the shape of the contour as a whole. The equations of gas dynamics in the hodograph plane are discussed. The Prandtl-Glauert rule applies only to thin aerofoils of low camber and at a small angle of attack in a stream of relatively low Mach number.