Concurrent vortex-shedding and surface-wave phenomena around a horizontal circular cylinder close to a free surface

A fully submerged horizontal circular cylinder close to a free surface moves horizontally below the free surface in a still fluid. Concurrent vortex-shedding and surface-wave phenomena are observed according to the relevant Froude number (based on the cylinder diameter) and the gap ratio (distance between the cylinder and the free surface non-dimensionalized by the cylinder diameter). Both constrained and unconstrained cases are considered in terms of the vertical motion of the cylinder due to the vortex shedding. Overall, associated with the vortex shedding, five different surface-wave phenomena are observed; no waves, small-amplitude waves, surging breaking waves, collapsing breaking waves (observed only in unconstrained cases), straight-streamline jet-like flows over the upper surface of the cylinder. In particular, for a constant gap ratio, the jet-like flow becomes steeper as the Froude number increases and, for a constant Froude number, the jet-like flow becomes steeper as the gap ratio decreases.