NACA-TR-1146

Abstract

<em>An investigation has been made in the Langley two-dimensional low-turbulence tunnel and in the Langley two-dimensional low-turbulence pressure tunnel of 6- and 10-percent-thick symmetrical circular-arc airfoil sections at low Mach numbers and several Reynolds numbers. The airfoils were equipped with 0.15-chord plain leading-edge saps and 0.20-chord plain trailing-edge flaps. The section lift and pitching-moment characteristics were determined for both airfoils with the flaps deflected individually and in combination, The section drag characteristics were obtained for the 6-percent-thick airfoil with the flaps partly deflected as low-drag-control flaps and for both airfoils with the flaps neutral. Surface pressures were measured on the 6-percent-thick airfoil section with the flaps deflected either individually or in appropriate combination to furnish flap load and hinge-moment data applicable to the structural design of the airfoil.</em> <br><em>The experimental results showed maximum lift coefficients of 1.95 and 2.03 for the optimum combinations of deflection of leading-edge flaps and trailing-edge flaps as compared with 0.73 and 0.67 for the plain 6- and 10-percent-thick airfoils, respectively. Scale effect on the maximum lift coefficients was, in general, small. The aerodynamic center was ahead of the quarter-chord point and moved toward the leading edge when either the leading-edge flap or the trailing-edge flap was deflected. Deflecting the leading-edge flap was more effective in extending the low-drag range to higher section lift coefficients than deflecting the trailing-edge flap. The maximum flap normal-force and hinge-moment coefficients were, respectively, 4.74 and 2.24 for the leading-edge flap as compared with 1.48 and -0.61 for the trailing-edge flap.</em> <br><em>A generalized method is developed that permits the determination of the chordwise pressure distribution over sharp-edge airfoils with plain leading-edge flaps and plain trailing-edge flaps of arbitrary size and deflection.</em>