VARIATION OF PEAK PITCHING-MOMENT COEFFICIENTS FOB SIX AIRFOILS AS AFFECTED BY COMPRESSIBILITY

摘要

Pressure-distribution tests of six NACA l6-series propeller sections with 1-foot chords were conducted in the NACA 8-foot high-speed tunnel to determine the compressibility effects on peak section pitching-moment coefficients. The data are presented as curves of peak section pitching-moment coefficient against Mach number, thickness ratio, and camber.nThe peak pitching-moment coefficients were found to occur in the regions of positive and negative stall. For these conditions, especially for the thicker airfoils and in the region of positive stall, the critical speed occurred at Mach numbers as low as 6.30 and marked changes of the peak moment coefficient occurred at Mach numbers as low as 0.53. Increases in thickness and camber were found to accentuate the compressibility effects on peak moment coefficient.