Bottom friction and time-dependent shear stress for wave-current interaction

Bottom shear stresses in the wave-current interaction case are calculated using a numerical turbulent-closure model of the K-L type, where K is the turbulent kinetic energy and L is the length scale of the turbulence. Parameterized results of the friction coefficient are obtained in the case of a rough turbulent flow, as presented by Soulsby et al. [14], and these are here extended to the case of a smooth turbulent flow. Several comparisons with experiments and other results presented in the literature, particularly by Tanaka and Thu [19], show close agreement. A new parameterization of the time-series shear stress is proposed that includes a local friction coefficient and yields better results than the parameterization suggested by Soulsby et al. [14].