Flow Control on a NACA 4418 Using Dielectric-Barrier-Discharge Vortex Generators

Streamwise oriented Dielectric-Barrier-Discharge plasma actuators were used on a NACA 4418 airfoil for flow separation control at Re-c = 35 k and 95 k. Rows of symmetric and asymmetric actuators were located on the fore section of the suction surface, which were designed to create counterrotating and corotating streamwise vortex arrays, respectively. These could completely reattach the flow in the downstream of the actuators for alpha < 18 deg at Re-c = 35 k, and for alpha < 16 deg at Re-c = 95 k. The drag coefficient was reduced by 63% at alpha = 14 deg and the lift coefficient increased by 67%, while the symmetric actuators performed slightly better than the asymmetric actuators overall. Streamwise vortices appeared to play a key role at low angles of attack, although the flow reattachment is believed to be primarily due to a strong suction into the plasma. Furthermore, these streamwise actuators outperformed a pair of spanwise actuators over the same chord-wise locations.