Aerodynamic performance changes of an airfoil modified with biomimetic spiky-vortex generators

An experimental study was conducted to investigate the aerodynamic characteristics and surface flow topologies of spiky-vortex generators (Spiky-VGs) placed on the National Advisory Committee for Aeronautics (NACA0012) airfoil. Within the scope of this study, aerodynamic force measurement and titanium-dioxide (TiO2) surface oil experiments were performed at a Reynolds number (Re) of 1.5 x 10(5). Moreover, TiO2 surface oil and three-dimensional (3D) smoke-wire flow visualization techniques were applied to Spiky-VG having a certain scale. According to the aerodynamic force measurement results, it was observed that model 1 (M1) Spiky-VGs increase the maximum lift coefficient (C-Lmax) by 7.6% compared to the base NACA 0012 airfoil. It was observed that model 2 (M2) increased the lift coefficient (C-L) by 9.9% at an angle of attack slightly above the stall angle of the baseline airfoil (alpha = 11 degrees) and delayed the onset of stall by approximately 1 degrees. Furthermore, the drag coefficient (C-D) of model 2 (M2) is lower than that of the base wing model and is about 14.5%, indicating improved aerodynamic performance. It was observed that the presence of Spiky-VGs leads to significant alterations in surface flow topology over the wing model, primarily owing to their geometric configuration. The findings demonstrate that Spiky-VGs, functioning as vortex generators, contribute to enhanced aerodynamic performance by modifying surface flow topology and improving flow characteristics. Hence, they can be considered as effective passive flow control devices for airfoil applications.