Abstract
This paper examines four different active flow control (AFC) airfoils employing fluidic actuators in a zero net mass flux configuration. Modifications to the base NACA 6421 airfoil are made to achieve the four AFC airfoil configurations. Suction and injection slots, positioned at different locations and orientations on the upper surface, provide the means of fluidic actuation. Computational fluid dynamics (CFD) simulations are conducted using the in-house FASIP CFD code, which is a validated RANS solver incorporating the Spalart-Allmaras (SA) turbulence model, a third-order WENO scheme for inviscid fluxes, and second-order central differencing for viscous terms. The investigation is conducted at a Mach number (M) of 0.10 and a Reynolds number Re of 2.6 × 10^6 under a simulated cruise conditions. Comparison with the baseline NACA 6421 airfoil demonstrate significant enhancements in lift and drag performance in three of the four AFC configurations studied. Examination of the isentropic Mach number plots reveal that having the suction slot located downstream of the suction peak, such as in AFC2 and AFC4, demonstrate lower power requirements than the configuration with the suction slot positioned in the vicinity of the suction peak, AFC1. Force component analysis conducted on all airfoils indicates a significant benefit of the jet reactionary force applied to airfoils with injection slots downstream of the suction slot, although the extent of this benefit may depend on the proximity to the suction slot and to the trailing edge. Furthermore, it is noted that AFC4, the configuration representing the Co-Flow Jet (CFJ), has the highest lift enhancement by airfoil circulation augmentation, substantially larger than AFC1, AFC2, and AFC3, however, the position and orientation of the suction slot reduces the overall lift increment. Both AFC2 and AFC4 achieve peak aerodynamic efficiency at relatively lower AoA of α = 10◦ and α = 5◦, respectively, with AFC2 and AFC4 achieving the highest efficiencies of (CL/CD)c = 91.91 and (CL/CD)c = 89.56 respectively. AFC1 achieves higher airfoil productivity values although at higher AoA than the alternative configurations, achieving the highest value of (CL^2/CD)c = 192.93 at α = 20◦. AFC2 demonstrates the highest effectiveness gain over the baseline NACA6421. It also has the highest efficiency gain, except at α = 5◦ at which point AFC4 peaks before steadily declining. AFC1 steadily increases in both effectivenss gain and efficiency gain until α = 15◦ . However, AFC3 is less effective and efficient than the baseline NACA6421 airfoil until α = 10◦