Active flow control for airfoil at low Reynolds numbers

Scaled model flight research has the potential of revolutionizing general aviation by reducing the number of flight tests required during the design and certification phase of airplanes. For dynamic scaling the Froude number has to be kept constant resulting in Reynolds number dissimilarity. The present study is concerned with the airfoil of the Aeromot 200S Super Ximango motor glider for which we built a dynamically scaled model (1:5). For a two-dimensional section of its wing, which has a modified NACA 64₃-618 airfoil, we investigated the Reynolds number dependence of the flow in the wind tunnel. The lift curve and the stall behavior were found to change noticeably when going from the full size cruise to the model cruise conditions. We simulated the flow for Reynolds numbers based on chord of Re=64,200 and 322,000. At Re=64,200, a sufficient part of the energy spectrum is resolved and turbulence modeling is not required. For this Reynolds number we investigated separation control by pulsed vortex generator jets and a plasma actuator. At the higher Reynolds number, Re=322,000, computer limitations prohibit direct numerical simulations and necessitate turbulence modeling. In the second part of the paper different hybrid turbulence modeling approaches are discussed and tested in 2-D calculations which allow us to identify the most promising approach for later 3-D simulations.