Effect of Mach Number on Airfoil Characteristics at Reynolds Number of 3,000

Abstract

The effects of Mach number at Re = 3,000 for different airfoils (NACA0012, NACA0002, NACA4412, NACA4402) with thickness and camber geometries are investigated for the propeller blade design of a Mars airplane. The present study shows that thin and cambered airfoils have larger variations in C_l than symmetric airfoils. As for thin airfoils, C_l at higher α has rapid increases when the M_∞ is low. This is because the flow separation occurs at the leading edge, and the flow is reattached on the airfoil surface. However, the rapid increase in C_l disappear as M_∞ increases because the flow reattachment does not occurs. As for cambered airfoils, the decrease in C_l becomes larger than that on the symmetric airfoils when M_∞ is higher. This is because C_p near the leading edge on the lower surface is smaller than that on the upper surface and the high-speed region on the lower side of the leading edge is enlarged as M_∞ increases. Then, the M_cr at Re = 3,000 tends to be larger than that predicted by linear theory.