Combined Wave and Current Flow Close to a Rippled Bed

This paper describes an experimental study carried out in a laboratory water tunnel to examine the velocity distribution in combined wave and current flow close to a rippled bed. The fluid velocities, both the horizontal and the vertical components, were measured simultaneously with a laser Doppler anemometer. The measurements indicate that the addition of a steady current causes a significant effect on the near-bed ensemble velocity field of the wave motion, owing primarily to the asymmetry of the lee-vortices that are formed during each half cycle of oscillation. On the other hand, the effect of adding a wave on the time-mean velocity field of a steady current is also significant in that the current experiences an enhanced roughness due to the additional turbulence produced by the wave motion.