Lift Distributions On Low Aspect Ratio Wings At Low Reynolds Numbers

Sathaye, Sagar Sanjeev

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Lift Distributions On Low Aspect Ratio Wings At Low Reynolds Numbers

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The aerodynamic performance of low aspect ratio wings at low Reynolds numbers applicable to micro air vehicle design was studied in this thesis. There is an overall lack of data for this low Reynolds number range, particularly concerning details of local flow behavior along the span. Experiments were conducted to measure the local pressure distributions on a wing at various spanwise locations in a Reynolds number range 30000 < Re < 90000. The model wing consisted of numerous wing sections and had a rectangular planform with NACA0012 airfoil shape with aspect ratio of one. One wing section, with pressure ports at various chordwise locations, was placed at different spanwise locations on a wing to effectively obtain the local pressure information. Integration of the pressure distributions yielded the local lift coefficients. Comparison of the local lift distributions to optimal elliptic lift distribution was conducted. This comparison showed a sharply peaked lift distribution near the wing tip resulting in a drastic deviation from the equivalent elliptic lift distributions predicted by the finite wing theory. The local lift distributions were further analyzed to determine the total lift coefficients vs angle of attack curves, span efficiency factors and the induced drag coefficients. Measured span efficiency factors, which were lower than predictions of the elliptic wing theory, can be understood by studying deviations of measured lift from the elliptic lift distribution. We conclude that elliptic wing theory is not sufficient to predict these aerodynamic performance parameters. Overall, these local measurements provided a better understanding of the low Reynolds number aerodynamics of the low aspect ratio wings.

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