Computational Evaluation of the Performance of Lifting Surfaces with Leading-Edge Protuberances

The leading-edge tubercles of humpback whale flippers have been shown to enhance hydrodynamic performance by increasing lift and decreasing drag poststall. To explore this effect, computational simulations of two models based on an idealized humpback whale flipper were conducted, one with a smooth leading edge and one with simulated leading-edge tubercles. Two different commercial computational fluid dynamics packages were used, STAR-CCM+ and Solid Works Flow Simulation, and the results were compared with experiment. Numeric lift predictions in the nonstall region were reasonably accurate (maximum error 6.6% between both codes), while lift predictions in the poststall, region were problematic. Numeric drag predictions in the early nonstall region were within experimental error for STAR-CCM+ using the Spalart-Allmaras turbulence model, while both codes exhibited drag prediction error in the stall region. Flow visualizations showed that the smooth flipper exhibited trailing-edge stall, while the simulated tubercle flipper stalled in the troughs, behind the leading notches, first. At high angles of attack, the simulated tubercle flipper still possessed significant regions of attached flow, which contributes to its ability to maintain increased lift poststall.