SEDIMENT TRANSPORT UNDER (NON)-LINEAR WAVES AND CURRENTS

Jan S. Ribberink, Irene Katopodi, Khaled A.H. Ramadan, Ria Koelewijn, Sandro Longo

Abstract


Two series of experiments were carried out in the Large Oscillating Water Tunnel of Delft Hydraulics, which was recently extended with a recirculation flow system. Combined wave-current boundary layer flows were studied with a mobile sand bed in the sheet flow regime. Detailed intra-wave concentration and velocity measurements were carried out and revealed a three-layer system, i.e. a pick-up layer, a sheet flow layer and a suspension layer. In the suspension layer time-lag effects of the sediment concentration led to sediment fluxes in upstream direction. The suspended sediment was more confined to the near-bed region than according to diffusion theories, most likely due to turbulence damping. The horizontal timedependent and net sediment fluxes were concentrated in the sheet flow and pick-up layer. Measured net sediment transport rates could be described as a linear relation with the third-order velocity moment near the bed.

Keywords


sediment transport; nonlinear waves; current

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