Supercritical aerofoils: a survey

This paper gives a brief survey of the various developments that have taken place in transonic aerodynamics which have finally led to the realisation of supercritical aerofoils, which are not only shock-free under design conditions but also behave satisfactorily under off-design conditions. The paper explains how an initial high curvature around the sonic point, followed by a relatively flat surface of small curvature on the top side, which is typical of supercritical aerofoils, is needed to generate shock-free flow. Typical results presented for a conventional aerofoil and a supercritical aerofoil bring out the features which distinguish them. A brief account of the various methods available for analysis and design of supercritical aerofoils indicating their relative merits is also given. The first-order effects on the pressure distribution over such aerofoils due to viscous effects, particularly on shock location, are also briefly touched upon. Finally the benefits that accrue from the use of supercritical wings are dealt with.