Experimental Investigation of a Wavy Leading Edge Cylinder

Flow over a humpback whale flippers bio-inspired wavy cylinder is experimentally investigated. Besides the smooth model, a selection of a set of 4 wave combinations (2 amplitudes x 2 wavelengths) is compared using pressure distribution and aerodynamic forces. The study is performed in a wind tunnel at Reynolds numbers ranging from 3.9 x 10(4) to 2 x 10(5), within the sub-critical regime. The most notable results show that, for the 12% wavelength, the 3% and 11% amplitudes have opposite effects, with a drag coefficient reduction of up to 25%, and an increase of up to 25%, respectively. Flow visualizations shows the formation of three-dimensional laminar separation bubbles and the action of counter-rotating vortex pairs, with a shift in the separation line and a change in the base pressure, which suggest the mechanisms behind drag variation.