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Modeling of net sediment transport rate due to wave-driven oscillatory flow over vortex ripples
Abstract A one-dimensional-vertical (1-DV) model is developed for predicting net ripple-averaged sediment transport rate over a rippled bed under wave-driven oscillatory boundary layer flows. This model is extended from a sheet-flow model developed by Yuan and Tan [52], which is able to account for the effect of wave nonlinearity (velocity skewness and asymmetry) together with a mild bottom slope. The rippled bed is conceptualized as a flat bed with a large bottom roughness accounting for the presence of ripples in modeling the boundary layer flow and sediment concentration. The vortex-shedding effect is incorporated into the model by adding a pick-up rate on top of the one induced by skin-friction turbulence. The model performance is good for 2-D ripples under periodic oscillatory flows, which are used for calibrating the model. We also showed that it is applicable for 3-D ripples and irregular oscillatory flows. In addition, this 1-DV model can capture some intermediate ripple- and period-averaged physical processes, e.g., cycle averages of velocity, sediment concentration and sediment flux, suggesting that the model correctly captures the underlying physics. The relative importance of vortex-shedding effect is shown to be controlled by ripple dimension, sediment grain size and the driving mechanisms for net sediment transport rates.
Modeling of net sediment transport rate due to wave-driven oscillatory flow over vortex ripples
Abstract A one-dimensional-vertical (1-DV) model is developed for predicting net ripple-averaged sediment transport rate over a rippled bed under wave-driven oscillatory boundary layer flows. This model is extended from a sheet-flow model developed by Yuan and Tan [52], which is able to account for the effect of wave nonlinearity (velocity skewness and asymmetry) together with a mild bottom slope. The rippled bed is conceptualized as a flat bed with a large bottom roughness accounting for the presence of ripples in modeling the boundary layer flow and sediment concentration. The vortex-shedding effect is incorporated into the model by adding a pick-up rate on top of the one induced by skin-friction turbulence. The model performance is good for 2-D ripples under periodic oscillatory flows, which are used for calibrating the model. We also showed that it is applicable for 3-D ripples and irregular oscillatory flows. In addition, this 1-DV model can capture some intermediate ripple- and period-averaged physical processes, e.g., cycle averages of velocity, sediment concentration and sediment flux, suggesting that the model correctly captures the underlying physics. The relative importance of vortex-shedding effect is shown to be controlled by ripple dimension, sediment grain size and the driving mechanisms for net sediment transport rates.
Modeling of net sediment transport rate due to wave-driven oscillatory flow over vortex ripples
Wang, Dongxu (Autor:in) / Yuan, Jing (Autor:in)
29.10.2019
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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