An analysis of available data on the local aerodynamic centres of aerofoils in two- and three-dimensional flow

Abstract

This report reviews existing information regarding the behaviour of the local aerodynamic centres of aerofoils, with a view to exposing the more important gaps in our knowledge, and, indicating the lines along which future research might most profitably be directed. Starting with the two-dimensional aerofoil in incompressible, viscous flow, for which aerodynamic centre position may be correlated with lift slope, the report passes on to examine the behaviour of the two-dimensional aerodynamic centre in compressible flow. Experimental data which have been analysed (relating to the subsonic and lower transonic regimes) are not in agreement with the predictions of potential flow theory; this suggests that the Reynolds number and transition position effects, associated with viscous flow, exert a powerful influence on the aerodsalamic centre. Considering next the locus of aerodynamic centres for wings of finite aspect ratio, the report discusses the various incompressible potential flow theories and their extension to the subsonic and transonic regimes of compressible flow, and collects in a series of figures, the published results of calculations by various investigators. A brief mention is made of supersonic theory. A further set of figures presents experimental data. No prescription can be given for determining exactly the behaviour of the local aerodynamic centres of a given wing, but in the concluding section of the report it is suggested how the reader may use the assembled data to make a reasonable guess.