Surface flow topology visualizations of wings with leading-edge tubercles under pitch, yaw and roll conditions

zhaoyu wei, T.H. New, Y.D. Cui

Last modified: 2016-03-22

Abstract


Flows past wings with leading-edge tubercles were visualized through surface oil visualizations by a mineral and engine oil solvent mixed with fluorescent pigment ZnS. One baseline and six wings with leading-edge tubercles were considered. The mean chord of all these NACA634-021 based wings is c=75mm and span is s=300mm. Wings with leading-edge tubercles were designed by modifying the cross-section of the baseline wing through a nonlinear shear transformation method. The planforms of the leading-edge tubercles were treated as sine waves with two different wavelengths, λ=0.25c and 0.5c, and three different wave amplitudes of A=0.12c, 0.05c and 0.025c. The experiments were conducted in a low speed close-circuit wind tunnel at a Reynolds number of Re=180k. The experiments were conducted under a combined pitch angle of 20°, yaw angle of 15° and roll angle = 15° condition to look into the behaviour of such leading-edge tubercles under drastic flow conditions. Surface oil visualization images for all the seven wings are shown above. Skewed wing tip separations across the wing span can be seen to exert significant flow disruptions for the baseline wing. In contrast however, the imposition of leading-edge tubercles appears to elevate the situation, depending on the exact configuration. In particular, the use of large wave amplitudes (regardless of the wavelength) is able to mitigate the large flow separations and reattachments seen for the baseline wing, presumably due to the favourable streamwise vortices produced by the leading-edge tubercles. Interestingly, the largest wave amplitude configuration also tends to lead to bi-periodic flow patterns behind the tubercle troughs. On the other hand, small-to-moderate wave amplitude configurations here do not appear to have much favourable influences upon the skewed flows along the wing spans.

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