Non-Equilibrium Sediment Transport Modeling - Extensions and Applications
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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The non-equilibrium sediment transport NEST modeling approach has been extended and applied in this chapter to simulate non-cohesive sediment transport induced by rapidly-varying transient flows, by coastal current and waves, in vegetated water bodies, and by overland flow. Even though different flow models are used in these cases, the sediment transport models are similar, with differences in sediment entrainment, adaptation length, and effective diffusivity. In the case of rapidly-varying transient flows, the generalized shallow water flow equations are adopted to consider interactions between flow, sediment transport and bed change. In the coastal context, the flow model adopts the phase-averaged shallow water flow equations with wave-induced radiation stresses coupled with a spectral wave transformation model, and the sediment transport model accounts for sediment entrainment and mixing diffusion and dispersion by currents and waves. In the case of vegetated channels, the vegetation drag and inertia forces are considered in the momentum equations and the sediment transport capacity is modified due to vegetation effect. For upland soil erosion, the overland flow is simulated using a 2-D diffusion wave model and the rillinterrill erosion due to raindrop splash and hydraulic shear is considered in the sediment entrainment. In addition, a general NEST model framework has been developed for simulating transport of cohesivenon-cohesive sediment mixtures, taking into account the effects of cohesive sediment flocculation, bed consolidation and interactions between cohesive and non-cohesive bed materials. Selected test cases demonstrate that the extended NEST models can reasonably reproduce the sediment transport and morphology evolution under these complex flow conditions.
- Physical and Dynamic Oceanography
- Hydrology, Limnology and Potamology