On the Role of Leading-Edge Bumps in the Control of Stall Onset in Axial Fan Blades

Abstract

Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge

Effects of leading-edge tubercles on wing flutter speeds

“…Subsequent numerical simulations also confirmed the finding through higher-fidelity numerical methods [16,17,18,19,20]. These were accompanied by experiments on both full-and semi-span rectangular planforms in either wind [21,8,22] or water tunnels [23].…”

Mimicking the humpback whale: An aerodynamic perspective

“…In the case of the TLE wing, it stalled at 14°or 15°. Post-stall simulations for AoA 20°showed that the TLE wings outperformed Corsini et al [75] studied the effect of TLE on symmetric NACA 0015 and cambered NACA 4415 airfoils. 3D numerical investigation was carried out using Open FOAM.…”

A Critical Review of Passive Noise Control Techniques in Industrial Fans

“…An assessment of the modified geometry on a cambered airfoil entailed the comparison of aerodynamic performance against the same geometry without a sinusoidal-shaped leading edge, as well as an uncambered airfoil. The sinusoidal-shaped leading edge modified the aerofoil lift coefficient during stall, with an early recovery of the aerofoil's aerodynamic work capability and a 30% gain in lift after stall for the WHALE4415 airfoil [43].…”

“…Recently, Corsini et al [43] presented a particular fan blade crenulation that they associated with humpback whales' abihty to execute very sharp rolls and loops under water. The crenulations were in the form of bumps on the leading edge of the whale's flukes.…”