A Effects of Reynolds Number and Leading-edge Roughness on Lift and Drag Characteristics of the NACA 653-418 PDF Download

Author: John H. Quinn
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 7

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Book Description
Tests were made in the Langley two-dimensional low-turbulence tunnels of an NACA 653-418, a = 1.0 airfoil section with roughness in the form of carborundum grains applied to the leading edge. Roughness grains having average diameters of 0.0003 and 0.0007 airfoil chord were applied to the leading edge of the wing, and lift and drag measurements were made for a range of Reynolds numbers from 0.23 to 3.0 x 106. From a comparison of data obtained in the present tests with data obtained in tests of the smooth wing, marked reductions in maximum lift coefficient were found to be caused by the roughness throughout the test range of Reynolds number. The drag coefficient at the design lift coefficient increased sharply and the lift-curve slope decreased rapidly at a critical Reynolds number that depended upon the size of the carborundum grains. This critical Reynolds number occurred at approximately 0.50 and 0.70 x 106 for the 0.0003- and the 0.0007-chord-diameter roughness grains, respectively. With roughness, a decrease in maximum lift coefficient as great as 0.2, a decrease in lift-curve slope of 0.028, and an increase in drag coefficient at the design lift coefficient of 0.0007 were observed at a Reynolds number of 1.0 x 106. For the smooth wing at the same Reynolds number, the maximum lift coefficient was 1.19, the lift-curve slope was 0.116, and the drag coefficient was 0.0077. At Reynolds numbers greater than 1.0 x 106, the scale effect on the lift and drag characteristics of the section with both degrees of roughness was generally in the same direction as the effect on the lift and drag characteristics of the smooth airfoil.