Numerical investigation of air jets for dynamic stall control on the OA209 airfoil

Abstract

Dynamic stall is one of the limiting cases for helicopter design. This report describes the design and numerical investigation of air jets for dynamic stall control. Prospective control devices were first investigated using 3D RANS computations to identify effective configurations and reject ineffective configurations. Following this, URANS investigations on the same grids verified that configurations had been selected which reduced the peaks in pitching moment and drag while preserving at least the mean lift and drag from the clean wing. The investigations used the DS2 test case on the OA209 airfoil, for which an extensive experimental database is available. As a comparison to the jets, a vortex generator configuration (LEVoG) for which experimental results at DS2 exist was also investigated. Two practical configurations using jets at 10% chord on the airfoil top were identified, and one practical configuration using a tangential slot at 10% chord on the airfoil top. Each configuration was evaluated for two injector total pressures, and for jets turned on for only a half-cycle. For the best configuration, a reduction in the pitching moment peak of 85% and in the drag peak of 78% were observed, together with a 42% reduction in the mean drag over the unsteady pitching cycle. A selection from the most successful configurations will be built into an airfoil model and tested in the DNW-TWG wind tunnel.