Investigation on the aerodynamic properties of an airfoil with biomimetic shark scale surface

Abstract This study examines the aerodynamic performance of a NACA 4412 airfoil that is covered with denticles, comparing it to a smooth NACA 4412 airfoil. The aim was to assess the lift-to-drag ratio of the airfoil utilizing biomimetic surfaces inspired by the dermal denticles of Isurus oxyrinchus . To achieve this, the airfoils were subjected to testing in a wind tunnel. Both the denticles-covered and smooth airfoils, measuring 355 by 184 mm, were equipped with 27 pressure taps distributed across three spanwise sections: the leading edge, upper surface, and lower surface. Nine flexible tubes were connected to pressure sensors for each row of static taps. Wind tunnel tests were conducted at various angles of attack (AOAs), ranging from −10.8° to 16.2° with an increment of 1.8°. Testing was carried out at wind speeds of 3, 6, and 9 m/s. Computational fluid dynamics (CFD) simulations were conducted on the smooth airfoil under identical conditions to validate the wind tunnel testing setup. The lift and drag coefficients were derived from the recorded static pressures. A comparison between the aerodynamic coefficients obtained from experiments and CFD simulations indicated that higher wind speeds are preferable for wind tunnel testing as they yield more consistent results. When examining the aerodynamic coefficients of the smooth airfoil compared to the denticle-covered airfoil, it was found that the latter generally produced higher lift and drag, resulting in a lower lift-to-drag ratio across different angles of attack and wind speeds. Specifically, at 3 m/s, the denticle-covered airfoil exhibited better lift at most AOAs, higher drag at certain AOAs, and improved lift-to-drag ratios. At wind speeds of 6 and 9 m/s, the denticle-covered airfoil demonstrated higher lift for all tested AOAs and increased drag for several AOAs, yet it consistently had lower lift-to-drag ratios. These findings point to the potential benefits of utilizing the denticle-covered NACA 4412 airfoil due to its enhanced lift characteristics at lower wind speeds. Further research is warranted to quantify the differences between the airfoil types.