The Calculation of the Total and Skin Friction Drags of Bodies of Revolution at Zero Incidence

SUMMARY. By means of the principles and assumptions used to calculate the profile drag of aerofoils a method is developed for calculating the total and skin friction drags of bodies of revolution at zero incidence. The method is applied to three bodies of different fineness ratio for three Reynolds numbers and three transition points. From the results curves are drawn showing the variation of total drag for a ra.nge of fineness ratio (00 to 3 : 1), Reynolds number (10 6 to 10 8) and transition point position (0 to o· Sl). Comparison with experimental results sho,vs satisfactory agreement. Interesting deductions are: form drag (a) t t l d == O· 4 djl, approx. o a rag (b) Given the volume and transition point position the fineness ratio for which the drag is least is about 5 : 1. (c) Given the frontal area and transition point position the fineness ratio for which the drag is least is about 3 : 1. x y r ~ 1 d A f(d/l) Do U u o A 15* distance along surface froll1 stagnation point or distance along centre line of wake, distance measured normal to surface or normal to centre line of wake, radius of cross section of body, distance measured parallel to axis of body from stagnation point, angle between tangent to generator and aXls of body, length of body, maximum diameter of body, surface area of body, Ajl2, velocity of undisturbed stream, velocity at edge of boundary layer or wake, velocity in boundary layer parallel to surface or in wake parallel to centre line, boundary layer thickness or radius of cross section of wake,