Hughes friction line

The Hughes friction line is G.H. Hughes’s 1954 two-dimensional turbulent flat-plate friction formulation, C_F0 = 0.066 / (log10 Re - 2.03)^2, derived from plank and pontoon tests to Reynolds numbers near 3e8. Hughes paired it with the form-factor concept: total viscous resistance is (1+k) times the flat-plate friction, so C_T = (1+k) C_F0 + C_W. This form-factor approach passed into the ITTC-1978 method, although ITTC-1978 uses the ITTC-1957 line rather than Hughes’s own line as the friction basis. The Hughes line gives lower values than ITTC-1957 because the ITTC line already carries a deliberate correlation margin.