Vortices were not present on the unmodified NACA 0009 at any time, making it a unique consequence of sharp leading edge modification. It appeared that the formation of vortices on the suction surface of the sharp leading edge airfoils played a role in either boundary layer reattachment or viscous drag mitigation. Below Re = 3 x 10^4, however, peak efficiency was attained by the modified airfoils, with NACA 0009-03 having the highest peak at Re = 2 x 10^4 and NACA 0009-05 having the highest peak at Re = 1 x 10^4. The unmodified NACA 0009 offered the highest lift and the least drag compared to the modified airfoils at Reynolds numbers between 3 x 10^4 and 5 x 10^4, which caused it to also have the highest efficiency peak within that range. ![]() A sharp leading edge in this study is defined as a leading edge where the radius of curvature is zero. Modifications were made to the NACA 0009 airfoil according to the NACA Modified 4-Digit algorithm developed by Stack and von Doenhoff, with one version having a sharp leading edge (NACA 0009-03) and another having a sharp leading edge with the location of maximum thickness moved to its mid chord (NACA 0009-05). The Langtry-Menter 4-equation Transition SST model was employed to solve the flow field. In this numerical study, a 2D method of simulating the behavior of such flows over a symmetric NACA 0009 airfoil was demonstrated at low ( 2 x 10^4 ≤ Re ≤ 5 x 10^4) Reynolds numbers and compared against experimental data. This gives rise to flow phenomena that deviate significantly from those at higher Reynolds numbers. A consequence of shorter chord length wings, lower flight speeds, and lower density atmospheres is that such flows experience a dominance of viscous forces over inertial forces, producing lower chord-based Reynolds numbers. Abbott, and Milton Davidson, March 1942 has been corrected and included in the present paper, which supersedes the previously published paper.The rise of microelectronics has paved the way for the development of small-scale unmanned aerial vehicles (UAVs) that can be employed for a number of military and scientific applications. Much of the data given in the NACA Advance Confidential Report entitled "Preliminary Low-Drag-Airfoil and Flap Data from Tests at Large Reynolds Number and Low Turbulence," by Eastman N. The NACA 6-series airfoils also have favorable critical-speed characteristics and do not appear to present unusual problems associated with the application of high-lift and lateral-control devices. Airfoils permitting extensive laminar flow, such as the NACA 6-series airfoils, have much lower drag coefficients at high speed and cruising lift coefficients than earlier types-of airfoils if, and only if, the wing surfaces are sufficiently smooth and fair. The data indicate that the effects of surface condition on the lift and drag characteristics are at least as large as the effects of the airfoil shape and must be considered in airfoil selection and the prediction of wing characteristics. Problems associated with lateral-control devices, leading-edge air intakes, and interference are briefly discussed. Available data on high-lift devices are presented. The report includes an analysis of the lift, drag, pitching-moment, and critical-speed characteristics of the airfoils, together with a discussion of the effects of surface conditions. Data and methods are given for rapidly obtaining the approximate pressure distributions for NACA four-digit, five-digit, 6-, and 7-series airfoils. The general methods used to derive the basic thickness forms for NACA 6- and 7-series airfoils and their corresponding pressure distributions are presented. Detail data necessary for the application of NACA 6-serles airfoils to wing design are presented in supplementary figures, together with recent data for the NACA 24-, 44-, and 230-series airfoils. Most of the data on airfoil section characteristics were obtained in the Langley two-dimensional low-turbulence pressure tunnel. ![]() ![]() The flight data consist largely of drag measurements made by the wake-survey method. Summary of Airfoil Data Recent airfoil data for both flight and wind-tunnel tests have been collected and correlated insofar as possible.
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