VKI, Belgium, 1999. 33 p.Summary
A description of the micro-air vehicle (MAV) concept and design requirements is presented. These vehicles are very small and therefore operate at chord Reynolds numbers below 20000 where very little data is available on the performance of lifting surfaces, i.e., airfoils and low aspect-ratio wings. This paper presents the results of a continuing study of the methods that can be used to obtain reliable force and moment data on thin wings in wind and water tunnels. To this end, a new platform force and moment balance, similar to an already existing balance, was designed and built to perform lift, drag and moment measurements at low Reynolds numbers. Balance characteristics and validation data are presented. Results show a good agreement between published data and data obtained with the new balance. Results for lift, drag and pitching moment about the quarter chord with the existing aerodynamic balance on a series of thin flat plates and cambered plates at low Reynolds numbers are presented. They show that the cambered plates offer better aerodynamic characteristics and performance. Moreover it appears that the trailing-edge geometry of the wings and the turbulence intensity up to about 1% in the wind tunnel do not have a strong effect on the lift and drag for thin wings at low Reynolds numbers. However, the presence of two endplates for two-dimensional tests and one endplate for the semi-infinite tests appears to have an undesirable influence on the lift characteristics at low Reynolds numbers. The drag characteristics for thin flat plate wings of aspect ratio greater than one do not appear to be affected by the endplates. The effect of the endplates on the drag characteristics of cambered-plate wings is stilunder investigation. It is known, however, that endplates do have an effect on the drag and lift characteristics of a cambered Eppler 61 airfoil/wing.
