Revisiting wave friction factors for rough turbulent flow

The wave friction factor 𝑓𝑤 and the phase lead of the seabed shear stress over the free stream velocity 𝜑 for rough turbulent flow are revisited by utilizing the similarity theory used by Myrhaug (1989). Results are obtained for 𝑓𝑤 and 𝜑 by determining the similarity coefficients using the Dixen et al. (2008) data for large bed roughness. Comparisons are made with other experimental data and wave friction factor formulae. As a result, an approximation for 𝑓𝑤 by disregarding the phase 𝜑 is recommended covering a wide range of amplitude-to-roughness ratios.