Abstract:

ESDU W.S.00.03.03 discusses the flow around an aerofoil in inviscid flow and explains how the velocity and pressure distributions, and hence the forces on the aerofoil, can be obtained from a knowledge of the free-stream conditions and the pressure rise through a shock wave or the pressure drop through a Prandtl-Meyer expansion, provided the shock waves are attached. This is illustrated for a double-wedge section but its extension to curved sections is also considered. The methods based on that technique using data provided in the Volumes are discussed in terms of shock-expansion or simple-wave flow calculations or second- or first-order theories, and the relative accuracy of the methods is considered and illustrated with results for two thicknesses of aerofoils. The behaviour of the lift-curve slope, drag and aerodynamic centre position in subsonic and supersonic flows is compared. The causes of nose shock detachment and its consequences are discussed. The effects of viscosity are then outlined and the components of drag are defined - wave, skin friction and viscous form (together usually called profile), and base. The effect on profile drag (from the change in wave drag) resulting from the effective change in the profile shape due to the displacement thickness of the boundary layer is considered. The interaction between a shock and the boundary layer is discussed including the flow phenomena for a shock near the trailing edge, and the circumstances are indicated when separation is likely to occur. Base pressure is briefly considered and other data in the series are referenced.