Abstract

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 upper
and lower surfaces at (Re=25×103). Experimental study was also done on the
control of flow around (NACA 0015) airfoil of backward facing step with and
without 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 were
done in a low-speed wind tunnel in order to obtain the pressure distribution on the
airfoil surface and lift and pressure drag coefficients. The airfoils used in the
experimental study were the basic airfoil, airfoil of backward facing step on the
lower surface with and without bumps, and airfoil of backward facing step on the
upper surface with and without bumps. The theoretical results illustrate the benefit
of using bumps on the lower and upper surfaces of the (NACA4418) airfoil. The
laminar separation bubble was delayed. Also the theoretical and experimental
results show the benefit of using bumps inside the steps on the lower or upper
surfaces of the airfoil. The (Clmax) was increase by (25.04%) with respect to the
basic (NACA 0015) airfoil and by (7.14%) with respect to the airfoil with smooth
step 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) airfoil
and (5.86%) with respect to the airfoil with smooth step on the upper surface.