Abstract:

ESDU 87001 evaluates a simple semi-empirical method by comparing predictions made using it with tunnel data drawn from a wide range of sources. The method determines at low speed the contribution due to the integral of the local zero-lift pitching moments allowing for the effect of taper, and adds to that the contribution due to twist (both geometric twist and aerodynamic twist arising from any variation of camber along the span). Two methods for treating the twist contribution are given, one for linear twist and one for non-linear twist; in the latter case it is found that use of an equivalent linear twist is often satisfactory. Mach number corrections to the low speed contributions (both local and twist) are provided. The method applies to a wide range of cambered and twisted straight-tapered wings, either swept forward or back, provided local effective twist is less than 10 degrees and the flow is fully attached and wholly subsonic. It can be applied to wings with curved or cranked edges using the "equivalent planform" concept of ESDU 76003. Comparisons are shown of prediction with experiment for a wide range of aerofoils and of wings with various twist distributions. It is seen the method predicts pitching moment coefficient, based on mean aerodynamic chord, to within 0.005 for values below 0.02, and to within 15 per cent for values above 0.02. Two practical worked examples illustrate the use of the data, and a computer program that implements the method is available as ESDUpac A8701.