Author(s): Thuy T. T. Vu; Lam T. Nghiem; J. K. Seelam; P. Nielsen
Linked Author(s): Jaya Kumar Seelam, Thi Thu Thuy Vu
Keywords: Sediment transport; Waves and currents; Sand barriers; Rippled bed
Abstract: The paper summarizes morphology changes over rippled sand barriers under wave and wave combined current of 27 laboratorial experiments. Data of 4 wave conditions (H=10cm, T=1s; H=12cm, T=1s; H=12cm, T=1.5s; H=14cm, T=1.5s) and 6 currents (Q= 10, -10,20, -20,25, -25 l/s) including 4 cases of wave only were analysed. Sediment transport direction of the shorter period wave combinations is opposite to the current direction. In other words, q s is against wave propagation when waves and current are in the same direction; while q s is in the wave propagation direction when the waves propagate against the current. The q s -direction of sediment transport is not consistent in the combinations of longer period wave. The existing sediment transport formulae in a wave-current induced ripple bed morphology are assessed utilizing available laboratory data of wave, velocity, bed change and ripple dimensions. Five models work well and are widely used in non-breaking waves over rippled beds such as the diffusion model, the heuristic model, the grab and dump model of Nielsen (1988), Ribberink & Al-Salem (1994) and Nielsen’s (2006) were tested against experimental data. The results illustrate the challenges related to complicated vertical velocity distributions in combined wave-current flows and the relations between near-bed fluid velocities and sediment transport rates, even in 2DV flows.
Year: 2014