Calculation of profile drag of airfoils at low Mach numbers.

This paper investigates the accuracy of a particular method for calculating the profile drag of airfoils at low Mach numbers. The method consists of 1) calculation of the pressure distribution by any suitable method, 2) calculation of laminar flow near the nose by Thwaites' method, 3) calculation of transition by Michel's method (if it is not known a priori), 4) calculation of turbulent boundary-layer flow by Head's method, and, finally, 5) calculation of momentum deficiency in the far wake by means of the Squire-Young relation. Profile drag has been calculated by this method for several airfoils at various angles of attack and Reynolds numbers. The effects of transition and airfoil thickness on the profile drag are studied. Comparison of calculated and experimental values show generally good agreement. The rms error based on 88 calculated drag values is 2.7%.