Experimental Investigation of Slotted Airfoil Performance with Modified Slot Configurations

Abstract

The purpose of this experiment is to determine the effects of various slot configurations on the stall angle of attack for an airfoil similar to the NACA 653-618. The slot was used in an attempt to energize the boundary layer on the upper surface of the airfoil with high-velocity flow in order to keep the flow attached and consequently delay stall. A slotted airfoil design, constructed using mahogany and modeled from the NACA 653-618 airfoil, was tested to investigate the effect of a slot on lift and drag data. The test plan included experimentation on the following three airfoil configurations: a solid airfoil, a small slot configuration, and a large slot configuration. The experiments included collecting force balance and flow visualization data. Results indicate lift coefficients for the slotted airfoils are higher than the solid airfoil for all angles of attack greater than 15o. Below 15o, however, the slotted airfoils generate less lift. Data indicated that drag coefficients for the slotted airfoils were generally lower than those of the solid airfoil at low angles of attack. At angles of attack greater than 25o, the small slotted-airfoil generates significantly less drag than the other two airfoils. These trends in force balance data were corroborated by stall patterns determined using flow visualization tufts.