EXPERIMENTAL INVESTIGATIONS ON FLUIDIC CONTROL OVER AN AIRFOIL

摘要

This study presents the development of two fluidic actuators — namely, microjets and tangential blowing actuator (TBA), designed for flow separation control. The developed actuators are compact enough to fit inside an ONERA D profiled wing with a chord of 0.35 m. Test bench experiments showed that the microjets (resp. TBA) were able to produce exit velocities up to 330 m/s (resp. 60 m/s). These actuators were placed in the model and were tested in wind tunnels for various blowing rates. The investigations included the use of force balance measurements, on-surface flow visualization with pigmented oil, off-surface flow visualizations with smoke, surface pressure distribution measurements, and Particle Image Velocimetry (PIV). Most of the tests were performed at free-stream velocities between 20 m/s (for PIV) and 40 m/s, corresponding to Reynolds numbers in the range 0.47 x 10~6-0.93 x 10~6. The angle of attack varied from -2 to 20 degrees. Experiments were conducted using the naturally occurring laminar boundary layer as well as for a turbulent boundary layer. In such a case, rough strips were used in the vicinity of the leading edge. The present tests show the efficiency of these devices to delay separation and improve aerodynamic performances of the wing: for example, a maximum of 30% gain in Cl has been reached using the microjets. Both actuators tend to increase the lift coefficient Cl after stall and areas of separated flow have been eliminated by applying control, as suggested by flow visualizations and PIV velocity fields.