Formation Flight of Low-Aspect-Ratio Wings at Low Reynolds Number

This paper examines the application of formation flight to micro air vehicles with regard to possible power savings. Results of an experimental investigation on echelon formations using low-aspect-ratio (AR=2) flat plate rectangular wings at low Reynolds number (Re=35,000) are presented. One-, two-, and three-wing configurations are tested in a low-speed wind tunnel. To quantify the power savings by lift enhancement and drag reduction, the aerodynamic loads acting on each wing are measured using specific balances while the trailing wings of the formation are being traversed laterally and vertically in fine steps. In addition, the flowfields of the wing wakes are measured using particle image velocimetry. The force and flowfield measurements show that the optimal positions for lift enhancement appear at slightly spanwise overlapping between the leading and trailing wings.

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