Models of widely differing complexity have been used in recent years to quantify sediment transport processes for engineering applications. This paper presents a review of these model types, from simple eddy viscosity models involving the... more
Models of widely differing complexity have been used in recent years to quantify sediment transport processes for engineering applications. This paper presents a review of these model types, from simple eddy viscosity models involving the “passive scalar hypothesis” for sediment predication, to complex two-phase flow models. The specific points addressed in this review include, for the suspension layer, the bottom boundary conditions, the relationship between the turbulent eddy viscosity and particle diffusivity, the damping of turbulence by vertical gradients in suspended sediment concentration, and hindered settling. For the high-concentration near-bed layer, the modeling of particle interactions is discussed mainly with reference to two-phase flow models. The paper concludes with a comparison between the predictions of both a classical, one-equation, turbulence k-model and a two-phase flow model, with “starved bed” experimental data sets obtained in steady, open-channel flow.
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Surface waves travelling in water of finite depth may be scattered by a region of undulating bottom topography. The present study is concerned with the idealized two-dimensional situation in which long-crested surface waves are incident... more
Surface waves travelling in water of finite depth may be scattered by a region of undulating bottom topography. The present study is concerned with the idealized two-dimensional situation in which long-crested surface waves are incident upon a patch of long-crested regular bottom ripples. The principal question examined concerns the amount of incident wave energy that is reflected by the ripple patch. Linear perturbation theory is used to show that the reflection coefficient is both oscillatory in the quotient of the length of the patch and the surface wavelength, and also strongly dependent upon the quotient of the surface and bed wavelengths. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with the reflection of incident wave energy. A secondary question concerns the nature of the wave field in the immediate vicinity of the ripple patch. In resonant cases, it is shown how the partially standing wave on the upwave side of the...
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Above steep, wave-induced sand ripples, which occur extensively in shallow sea areas, the momentum transfer and suspended sediment dynamics are dominated by the formation and shedding at flow reversal of lee wake vortices. Since... more
Above steep, wave-induced sand ripples, which occur extensively in shallow sea areas, the momentum transfer and suspended sediment dynamics are dominated by the formation and shedding at flow reversal of lee wake vortices. Since two-dimensional models of this process are unduly complex for practical application, a simple, one-dimensional vertical (1DV), two-layer, model is presented here for the flow and transport