The Characteristic Research Of Lift Enhancement And Drag Reduction On Large Aerofoil

As one of the most important structural parts, aerofoil takes the most of the lift and quite a lot ofdrag from the aircraft；So it is very necessary to achieve the lift enhancement and drag reductionfurther through the aerodynamic optimization about the aerofoil. Furthermore taking the environmentprotection and economics into consideration, large civil aircraft and transport aircraft also needresearching on the technological breakthrough and innovation to satisfy the increasingly high standarddemand of the market. It can be predicted that it is very hard to meet the demand through theaerodynamic optimization to the existing large aircrafts just based on the traditional theory. So theactive flow control is bound to take the role of the technological breakthrough on the aircraftaerodynamic.As one of the very important research direction in vortex induced control, this paper take the liftenhancement and drag reduction as target, combining with the preliminary work of our group; activepulsed vortex generation with two different type orifices based on the vortex induction fromtraditional VG; the flow field characteristic, the three dimensional form of active vortex system,surface influence area in wake current were detailed analyzed.The wind tunnel experiment showed that the vortex system from Counter AVG has good wallattachment and self-sustained effective; under the flow near the wall, the fluid with high momentumin main stream has sufficient blending with sublayer of boundary layer to increasing the flow velocityin the bottom;in the flow far from wall, the active pulsed vortex system has intact structure after it’sgeneration, this can help it induced with target vortex in the surrounding flow to decay it’s strength. Itis very helpful to control the separation flow and wing tip vortex on the aerofoil with two of thesecharacteristics mentioned above.Applying the Counter AVG to aerofoil separation control. The increment of maximum liftcoefficient was up to10.3%,the stalling angel was delayed backwards by2°and pressure dragdecreased remarkably, the coefficient reduction was27.7%at the separation angle. On the wing tipcontrol, the maximum lift drag ratio increased by6%in the span of0°to8°；the strength of wingtip vortex decreased by20%，total pressure recovery coefficient increased by10%。Besides the active control, the traditional methods like Gurney flap,winglet were alsoinvestigated by seven hole scanning system, flow visualization, balance, including structureconfiguration and working parameter.