Effect of Using Bumps on Wings Aerodynamic Characteristics at Low Reynolds Numbers


The effect of using bumps on the aerodynamic characteristics of airfoil at low Reynolds numbers is presented in this research. A theoretical study was done on the (NACA 4418) airfoil consist of bumps that have radius (2% c) on the upperand lower surfaces at (Re=25×103). Experimental study was also done on thecontrol of flow around (NACA 0015) airfoil of backward facing step with andwithout bumps inside the step at (Re=4.4×105). Theoretically the (Fluent 6.3)package was utilized for simulating the flow around the airfoils. Experiments weredone in a low-speed wind tunnel in order to obtain the pressure distribution on theairfoil surface and lift and pressure drag coefficients. The airfoils used in theexperimental study were the basic airfoil, airfoil of backward facing step on thelower surface with and without bumps, and airfoil of backward facing step on theupper surface with and without bumps. The theoretical results illustrate the benefitof using bumps on the lower and upper surfaces of the (NACA4418) airfoil. Thelaminar separation bubble was delayed. Also the theoretical and experimentalresults show the benefit of using bumps inside the steps on the lower or uppersurfaces of the airfoil. The (Clmax) was increase by (25.04%) with respect to thebasic (NACA 0015) airfoil and by (7.14%) with respect to the airfoil with smoothstep on the lower surface. When using step and bumps on the upper surface the(Clmax) was increase by (16.85%) with respect to the basic (NACA 0015) airfoiland (5.86%) with respect to the airfoil with smooth step on the upper surface.