This paper studies the regression of a numerical two-dimensional flat plate friction line using the RANS method with the SST k - co turbulence model. Numerical simulations with different inlet turbulence kinetic energies are first conducted. Comparing with the experimental data, the finest grid and the appropriate inlet turbulence kinetic energy are selected to compute the fiat plate friction resistance at 14 Reynolds numbers. Two numerical friction lines are obtained by the least squares root fitting method and one similar to that of the ITTC-1957 line and the cubic polynomials in logarithmic scales, and the results are compared to the friction line proposals available in the open literature. Finally, the full scale viscous resistance predictions of DTMB5415, KVLCC2, SUBOFF are compared between the numerical friction line and the friction line proposals available in the open literature based on the form factor approach. It is shown that the form factor keeps relatively constant via the numerical friction line for the bare hull, but the form factor concept in extrapolating the model test results is not appropriate for appended hulls. It is suggested that for computing a form factor numerically, it is best to use a numerical friction line.
