Experimental Study on Dynamic Stall of Airfoil in Rotor Reverse Flow Region

The large reverse flow region of the rotor with a high advance ratio is an important factor that affects performance improvement helicopters. This paper examines dynamic stall airfoil in to develop set pressure measurement systems for low region. pitch oscillation experiment NACA0018 and out has been carried out, influence motion parameters on stalls studied. results show more likely under static conditions invariant Reynolds number. After occurs, lift coefficient decreases slowly increase angle attack (about 10% forward state). Under environment, pitching cycle, quarter chord moment alternates between positive negative frequently during reverse-blowing. sensitive changes than normal flow, there marked difference. alternating significant: greater amplitude, moment. In reverse-blowing state, reduced frequency, increases significantly.