Effect of Relative Flap Length on Aerodynamic Performance of the Airfoil

Taking the NCA0018 airfoil as the benchmark airfoil,the effects of relative flap length(0.2,0.3and 0.4)and relative slot width(1.0%,1.5% and 2.0%)on the airfoil flow field and resistance properties were numerically studied using Fluent software,with focus on the effects of relative flap length on the airfoil areodynamic performance.Results show that the existance of flap helps to not only improve the airfoil stall characteristics,but also improve the aerodynamic performance of the airfoil,due to its impact on development and variation of the main vortex around the airfoil.For flap airfoil,the stall angle of attack within the scope of study is greater than that of the benchmark airfoil,and when the angle of attack is less than the stall angle of attack,the lift coefficient of flap airfoil will be less that of the benchmark type,and both the drag coefficient and the maximum lift coefficient will be higher than benchmark airfoil.The stall angle of attack reduces gradually with the rise of reltive flap length.When the angle of attack is close tothe stall angle of attack,the lift coefficient increases first and reduces later on.For a certain length of flap,the lift coefficient reduces with the rise of relative slot width.