Experiments on Flow Control of the Rotor via Synthetic Jets

Principle experiment for the synthetic jet control effects on the aerodynamic characteristics of the rotor in forward flight were conducted with low rotor rotation speeds and free stream velocities. To ensure the structural strength of the rotor and the enough interior room for installing the actuators, a particular blade with a frame-covering structure was designed and processed. To measure the synthetic jet control effect on the rotor in dynamic stall, the aerodynamic forces and sectional velocity field were measured by using the six-component balance and the Particle Image Velocimetry (PIV) system in the wind tunnel respectively. The experimental results indicated that the synthetic jet has the capability to delay flow separation over the blade and to improve aerodynamic characteristics of the rotor. Furthermore, flow control effects of synthetic jets on rotor's aerodynamic characteristics were experimentally investigated with different jet parameters, such as jet locations, jet angles and excitation voltages, and some meaningful conclusions were obtained. In forward flight, the jet closer to the leading-edge of the blade is more effective in improving aerodynamic characteristics of the rotor. The jet with 90° inclined angle could bring out the most increment of the rotor normal force, while the jet with 30° inclined angle has the best control effects on preventing flow separation in the retreating side. In general, the synthetic jet with 30° inclined angle is more appropriate for preventing dynamic stall of the helicopter rotor.