Enhancing the hydrodynamic performance of a tapered swept-back wing through leading-edge tubercles

The hydrodynamic benefit of implementing leading-edge (LE) tubercles on wings at very low Reynolds numbers (Res) has not been thoroughly elucidated to date, though their benefits at relatively higher Res are well-studied. Through wind tunnel testing at Re = 5.5 × 10⁴, we found that the LE tubercles increase the lift at all pitch angles tested and slightly reduce the drag at a pitch angle of 4° < α < 10°, which finally results in a significant hydrodynamic performance enhancement at lower pitch angles. Flow visualization reveals that the hydrodynamic performance enhancement is due to the favourable attached flows downstream of the tubercle peaks. The attached flows are believed to be closely related to the downwash and momentum exchange within the boundary layers, which originate from surface and streamwise-aligned counter-rotating vortex pairs (CVPs).