A general method for developing friction factor formulas under supercritical conditions and in different geometries

A general method for developing friction factor formulas in different geometries and under supercritical conditions was set up in this paper. The method was based on the two-layer wall function theory which could account for both the laminar viscous layer and turbulent layer. This characteristic led to its good agreement with empirical correlations in a wide range of Reynolds numbers, especially the prediction accuracy was improved at low Reynolds numbers in comparison with the previous work. This method could be extended to the flows over rough surfaces or with axial pressure gradient as long as the appropriate wall function is provided. Moreover, the wall function is based on Van Direst transformation which could take account of the fluid property variation across the boundary layer and thus the friction formula could be applied to supercritical flow. This formula could explain the special features of friction coefficient and showed good agreement with the experimental data performed by Nuclear Power Institute of China.