Measurements of wave-induced steady currents outside the surf zone

Abstract

Experimental measurements of the steady current induced by progressive regular waves outside the surf zone are reported and discussed herein. The experiments have been conducted in a large wave flume to minimize scale effects. The velocity data were acquired using Acoustic Doppler Velocimeters. It has been observed that the mean velocity profiles have a pronounced dependence on the wave period. As it decreases, the mean velocity just below the wave trough increases in the offshore direction while close to the bottom it increases in the onshore direction. The observed qualitative trend is different from that predicted by the theory and also from that reported by other experimental campaigns. The presence of turbulence in the bottom boundary layer along with wave asymmetry partially explain these differences. However, other experimental data in the literature agree with the present results.

Keywords:

• Boundary layer
• Eulerian mass transport
• sea wave
• undertow
• velocity measurement

Acknowledgement

This work has been supported by the European Community's Sixth Framework Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB III within the Transnational Access Activities, Contract no. 022441.