Waves plus currents crossing at a right angle: Experimental investigation

Abstract

The hydrodynamics generated by a regular wave field perpendicularly superimposed to a steady current is investigated by means of laboratory experiments. The flow structure is analyzed by measuring the velocity profiles using a micro Acoustic Doppler Velocimeter. Three cases are considered: current only, waves only and waves plus current. Different bottom roughnesses are used, and the apparent roughness ks is estimated for each condition. In the presence of a small roughness, the superposition of the waves on the current causes an increase of the current velocities close to the bottom, thus generating a decrease of the apparent roughness with respect to the case of the current only. On the other hand, when a large bottom roughness is present, the waves force a decrease of the current velocity close to the bottom and, in turn, an increase of the apparent bottom roughness. Such a behavior seems related not only to the roughness but also to the flow regime (i.e., laminar or turbulent) within the wave bottom boundary layer. Copyright 2006 by the American Geophysical Union.