NASA-TN-D-7428

Abstract

An investigation was conducted in the Langley low-turbulence pressure tunnel to determine the low-speed two-dimensional aerodynamic characteristics of a 17-percent-thick airfoil designed for general aviation applications. The results are compared with a typical older NACA 65 series airfoil section. Also, a comparison between experimental data and predictions, based on a theoretical method for calculating the viscous flow about the airfoil, is presented. The tests were conducted over a Mach number range from 0.10 to 0.28 and an angle-of-attack range from -10⁰ to 24⁰. Reynolds numbers, based on the airfoil chord, were varied from about 2.0 X 10⁶ to 20.0 X 10⁶. <br>The results of the investigation indicate that maximum section lift coefficients increased rapidly at Reynolds numbers from about 2.0&#160;&#215; 10⁶ to 6.0&#160;&#215; 10⁶ and attained values greater than 2.0 for the plain airfoil and greater than 3.0 with a 20-percent-chord split flap deflected 60&#176;. Stall characteristics were generally gradual and of the trailing-edge type either with or without the split flap. At a lift coefficient of 1.0 (climb condition) the section lift-drag ratio increased from about 65 to 85 as the Reynolds number increased from about 2.0&#160;&#215; 10⁶ to 6.0&#160;&#215; 10⁶. Maximum section lift coefficients were about 30 percent greater than that of a typical older NACA 65 series airfoil section and the section lift-drag ratio at a lift coefficient of 0.90 was about 50 percent greater. Agreement of experimental results with predictions based on a theoretical method which included viscous effects was good for the pressure distributions as long as no boundary-layer flow separation was present, but the theoretical method predicted drag values greatly in excess of the measured values.