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Summary: The effect of Reynolds number on the aerodynamic characteristics of a low-drag airfoil section tested under conditions of relatively high stream turbulence was determined by tests in the LMAL 7- by 10-foot tunnel of the NACA 653-418, a = 1.0 airfoil section with a split flap having a chord 20 percent of the airfoil chord. The Reynolds number ranged from 0.19 to 2.99 x 106; the Mach number attained was never greater than 0.10. The data are presented as curves of section angle of attack, section profile-drag coefficient, and section pitching-moment coefficient against section lift coefficient for various flap deflections. The maximum lift coefficient increased with Reynolds number. Deflecting the flap added an increment of maximum lift coefficient that seemed to be almost constant at all Reynolds numbers. The slope of the section lift curve with flap deflected showed no consistent variation with Reynolds number, although the slope of the section lift curve for the plain airfoil increased up to a Reynolds number of about 1.0 x 10 6 and then remained nearly constant up to a Reynolds number of about 3.0 x 106, the limit of the tests. For flap deflections about 15°, the slope of the section lift curve decreased with increase in flap deflection. The section drag coefficient with flap deflected remained almost constant with Reynolds number of about 0.8 x 106 and then remained nearly constant to a Reynolds number of about 3.0 x 106.
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Summary: An investigation in two NACA wind tunnels has determined the effect of Reynolds number and stream turbulence on the lift and drag characteristics of a low-drag airfoil, the NACA 653-418, a=1.0 section, particularly at low Reynolds numbers, to give an indication of the performance of low-drag wings in low-scale tests. The results are correlated with similar data for the same airfoil section in the NACA two-dimensional low-turbulence pressure tunnel to provide data over a range of Reynolds number from 0.19 to 9.0 x 106. Large increases in minimum drag coefficient were found as the Reynolds number decreased. This effect was particularly marked at Reynolds numbers below 1.5 x 106. At Reynolds numbers below 1.5 x 106, stream turbulence had little effect on the drag characteristics of the NACA 653-418 airfoil section when compared on the basis of test Reynolds number but, at higher Reynolds numbers, stream turbulence had a detrimental effect on drag. Large decreases in maximum lift coefficient were found with decreasing Reynolds number; most of this decrease was encountered at Reynolds numbers above 2.0 x 106. Marked differences in maximum lift were apparent between the results obtained at high and low turbulence. When compared on the basis of effective Reynolds number, however, fair agreement was reached between the data obtained under both turbulence conditions.
Reproductions of reports, some declassified, of research done at Langley Memorial Aeronautical Laboratory during World War II. The order of reports does not represent when they were chronologically issued. Reference to the original version of each report is included.
February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index.
On the road toward a history of turbulence, this book focuses on what the actors in this research field have identified as the “turbulence problem”. Turbulent flow rose to prominence as one of the most persistent challenges in science. At different times and in different social and disciplinary settings, the nature of this problem has changed in response to changing research agendas. This book does not seek to provide a comprehensive account, but instead an exemplary exposition on the environments in which problems become the subjects of research agendas, with particular emphasis on the first half of the 20th century.
The aerodynamic characteristics of 19 isolated tail surfaces have been determined by wind-tunnel tests and tests have also been made of rectangular airfoils of various aspect ratios with and without double end plates of various shapes. Thes data from these tests have been collected and analyzed.