A Note on the Aerodynamic Design of Thin Parallel-Sided Aerofoil Sections.

The familiar families of aerofoil section pervade all of contemporary aero and hydrodynamic design. They are used for parts of flight or marine systems intended to produce lift with minimum drag. They are also widely used as basically non-lifting fairings for bluff objects where it is desired to minimise drag and flow unsteadiness. However there are many circumstances where a conventional aerofoil section is not necessarily the optimum shape for a fluid swept, approximately two dimensional, object. The aim of the investigation reported here is to give some guidance as to the selection of suitable leading and trailing edge fairings for two dimensional flat plates. The overall thicknesschord ratio range considered is 2 to 6 which covers most of the practical applications. The investigation is limited to incompressible flow in the Reynolds number range 10 to the 5th power to 10 to the 7th power although the results should be directly applicable to sub-critical compressible conditions. A series of fairing shapes was investigated using two readily available aerofoil analysis computer programs. The programs were used as a numerical wind tunnel. A series of shapes was tested and, based on an analysis of the results and physical reasoning, further shapes were derived and computed.