Wave-current interaction at an angle 2: Theory

A theoretical model is presented to describe the current velocity within and outside a wave-current boundary layer and to quantify the associated bed shear stresses for wave-current interaction at an arbitrary angle. The model assumes that the wave-induced bed shear stress in the combined flow varies sinusoidally with time while the current-induced bed shear stress follows an eddy viscosity concept. The computational procedure is given for both depth-averaged and reference-point current-based computations. Unlike other analytical models proposing different coefficients for different problems, the present model uses the same set of equations and coefficients to describe wave-current flows at any angle under any flow regime. This model agrees better with both field measurements and laboratory data than existing theoretical models. The model indicates that the wave-current interaction angle is not significant for wave-current flow properties.