The turbulent wave boundary layer under a free stream circular orbital motion

This paper presents a simple model of the turbulent wave boundary layer for the case where the orbital motion formed by the waves just outside the boundary layer is circular. The analysis is based on the integral momentum method. It turns out that the wall friction under such a flow is larger than the similar 2D-case. It is demonstrated that even though the motion is quite different, the wall friction predictions are not significantly different from the 2D-case, where the orbital motion follows a straight line: the bed friction increases by 15–40% for the circular orbit case, depending on roughness and orbital radius. The analysis includes the case of a weak current superposed the waves. For this case, the flow resistance for the current increases by around 30–55% for a circular orbit compared to a straight motion back and forth.