Study On FlowSeparation Control And Application Of Bionic Wavy Edge Airfoil

Leading edge protrusion humpback whales with the limb like pectoral fins, biological properties provide a strong power for its prey rotary for inspiration. Thus in order to carry out the NACA634-021 bump leading edge airfoil aerodynamic characteristics, experimental study on the mechanism of flow field characteristics and concave convex front flow control; on the basis of the airfoil DU40, typical DU18 bionic concave convex flow control aerodynamic experimental study and calculation of flow field study; at the same time for the experimental study of bionic concave convex blade front edge and smooth blade.This paper based on the airfoil for the NACA634-021 (fin and humpback whales side cross-sectional geometry similar) as the base type smooth and wavy wing segment leading edge wing segment model, the 0°-90° angle of attack and Reynolds number 5 × 104, using five-component force balance measurements and particle image velocimetry (PIV) were measured in the wind tunnel in lift and drag, torque and other aerodynamic characteristics of airfoils and three-dimensional flow field, to carry out the validity of the method and associated bionic wavy edge experimental study of the mechanism. The results showed that:compared with the smooth wing section, wing leading edge section of the wavy more gentle stall characteristics, stall after a significant improvement in aerodynamic characteristics, which increase the maximum lift coefficient of up to 18%, the maximum lift-drag ratio increased by 12% drag coefficient is reduced by 10% in the 30°-80°angle of attack the leading edge of the area still has a wavy effect; through analysis of the wave front wing stall control mechanism is:when the air flow around the wave front after the air is guided around the convex peak exercise, on both sides of each peak of a pair of counter-rotating streamwise vortex structure, the scope of the vortex structure in the boundary layer is not limited, but also strengthened the internal boundary layer and external potential flow of momentum exchange, thus enhancing the airfoil’s ability to withstand the adverse pressure gradient, reducing the negative pressure suction side of the gradient, making the flow separation delay, stall can be delayed. At the same time the change trend of the amount vortex were analyzed in 17°～25°Angle, which changes in the very small, making the airfoil stall gently。On the flow control mechanism of the wavy wing, analyzing the ratio of effective height and boundary layer on the wavy wing, found that less than land the range 0.1～0.5 can effectively changing the stall characteristics of the airfoil and the role is similar to micro vortex generatorThe experimental study on the aerodynamic characteristics of the DU40 and wavy wing DU40-25wavy, DU40-1 lwavy and DU18 and wavy wing DU18-25wavy, DU18-1 lwavy showed that in the high angle of attack area wavy wind airfoils have improved lifting force coefficient, aerodynamic lift at low angles of attack area 11wavy airfoil has more advantages compared to the other two kinds.Calculation of DU40 and wavy wind airfoils DU40-25wavy, DU40-11wavy and DU18 and wavy wind airfoils DU18-25wavy, DU18-11wavy at a low angle of attack and flow field and the pressure coefficient distribution shows that wavy wind airfoils has a great impact on the distribution of pressure coefficient in the low angle region, because of the influence of wavy wind airfoils attack weaker smaller increase in pressure difference, the high angle of attack area due to increase of the streamwise vorticity wavy wind airfoils caused by the pressure difference coefficient, at the leading edge airfoil increases, increases lift coefficient. In addition,11wavy airfoil increased, showed more excellent aerodynamic performance.The smooth blade and wavy blades were test on the double blade experimental platform in the wind tunnel. The results show that:the wavy front blade, in the same coming flow wind speed and tip speed ratio respectively torque increase 15.6%, thrust decreases by 9.7%, increase power factor reach 22% than the smooth blade.