Experimental Exploration of Bioinspired Planar Wingtip Devices for a Flat-Plate Wing in the Low Reynolds Number Regime.

This study investigates the use of planar wingtip attachments to improve the lift generating performance of low aspect ratio (AR) flat-plate wings in the low Reynolds number (Re) range (<105). Inspired by nature's solutions, the slotted wingtip feathers of high lift wings as seen in eagles, we tested different configurations of wingtip attachments, ranging from a base plate with no attachments to plates with one, two, or four attachments for Re=8×104−15×104. The lift-to-drag (L/D) ratio, a commonly used metric for gauging the aerodynamic performance, shows that the configuration with four attachments (4A) has the superior performance. In the case of ARs of 1.0 and 1.5, the 4A configuration returns an average improvement of 20% and 7% over the base plate, respectively. The Oswald's efficiency factor (e), calculated for the experimental cases, is varied from a low 0.24 to more typical values of 0.86. The force per unit volume parameter is used to compare the performances of the modified wings and to take into account the weight added by the attachments. The results obtained demonstrate that the 4A configuration offers superior performance compared to the weight gained because of the addition of the attachments. [ABSTRACT FROM AUTHOR]