Abstract:
Summary.--The stalling properties of some thin nose-suction aerofoils already tested have been examined, and further theoretical investigations have been carried out on thin aerofoils specially designed to give high lift with nose-slot suction. In Part I, the experimental results from stalling tests on thin nose-suction aerofoils are compared and the design features of the tested aerofoils are analysed. The aero foils include the 8 per cent thick Lighthill and Glauert sections specially designed for nose-slot suction, the 8 per cent thick H.S.A. V section with distributed suction through a porous nose, and some conventional sections of moderate thickness tested in Germany with slot suction at various positions on the nose. The Lighthill and Glauert aerofoils proved quite good without suction, but the increments in CL max due to suction were rather disappointing. The H.S.A. V aerofoil with distributed suction promises to be more economical as regards suction quantities for delaying the stall at full-scale Reynolds numbers, but this needs further confirmation. Part II describes a theoretical exploration of possible thin nose-slot aerofoils specially designed to have an abrupt fall in velocity where suction is to be applied on the upper surface of the nose. In an attempt to obtain better sections as regards a late stall at practical suction quantities, various symmetrical and cambered shapes were designed by a simple approximate method and the effect of sink action was also estimated. Low-speed stalling tests are to be made on one of the new cambered sections (D.2/4) in order to determine whether the considerable improvements expected are in fact achieved. The effect of the unusual nose shape on the high-speed performance of the section will also need to be examined. The theoretical formulae required for the calculation of the velocity distribution and lift of an aerofoil with a sink on its surface, and some detailed notes on the design of the Glauert nose-slot aerofoil, are given in the Appendices.
