The Relation between the Skin Friction Drag and the Spin Reducing Torque

Abstract : On certain simplifying assumptions, a relation between the skin friction drag and the spin reducing torque or axial couple is deduced. On the basis of measured values of the axial couple coefficient the skin friction drag coefficient is deduced and compared with the measured total drag. A method is derived for utilizing the measured values of the axial couple coefficient to estimate the skin friction drag coefficient.