Exploratory Wind-Tunnel Investigation of the Effectiveness of Area Suction in Eliminating Leading-Edge Separation Over an NACA 64(1)A212 Airfoil

An exploratory investigation was made in the Langley two-dimensional low-turbulence pressure tunnel on an NACA 641A2l2 airfoil with various extents of permeable surface area between the leading edge and l2.5 percent chord to determine the effectiveness of area suction in eliminating leading-edge separation at high lift coefficients. Lift and internal pressure measurements were obtained at a Reynolds number of l.5 x 1,000,000 for a range of flow coefficients from 0 to 0.008. Airfoil surface pressures were measured over a range of angles of attack from 4.1 deg to 18.3 deg with the upper surface porous to 4.5 percent chord. The results obtained indicate that not only was leading-edge separation prevented, but also turbulent separation moving forward from the trailing edge was delayed. The maximum effectiveness was obtained at a flow coefficient of 0.0018 with the upper surface porous to 4.5 percent chord. With more than 4.5 percent chord permeable, the maximum section lift coefficient c sub l sub max of the airfoil was not changed appreciably, but the flow coefficient required to obtain c sub l sub max was considerably increased. It was also determined that for this airfoil at a similar Reynolds number the maximum section lift coefficient is about the same as that for the airfoil with a leading-edge slat.