The flow over asymmetrical ripples: an experimental investigation on the hydrodynamic behaviour

This paper reports on an experimental campaign focused on the hydromorphodynamics induced by sea waves propagating over a sloping sandy bed. The slope triggers a flow asymmetry that reflects on the bedform characteristics. Hydrodynamic characteristics have been acquired by means of a Vectrino Profiler at two measurement sections, one located over the sloping bed, the other at the plane bottom. The velocity measurements showed that waves are strongly skewed, with flat, wide troughs and sharp crests. As a consequence, phase averaged velocity profiles exhibit onshore velocities greater than offshore ones. An offshore-directed steady current occurs, which near the bed is strongly influenced by the ripple-generated lee wake vortices.