Rivers often witness non-uniform bed load sedim ent transport. For a long tim e, non-uniform bed load transport has been assum ed to be at capacity regime determined exclusively by local flow. Yet whether the capacity...Rivers often witness non-uniform bed load sedim ent transport. For a long tim e, non-uniform bed load transport has been assum ed to be at capacity regime determined exclusively by local flow. Yet whether the capacity assumption for non-uniform bed load transport is justified remains poorly understood. Here, the relative time scale of non-uniform bed load transport is evaluated and non-capacity and capacity models are compared for both aggradation and degradation cases with observed data. As characterized by its relative time scale, the adaptation of non-uniform bed load to capacity regime should be fulfilled quickly. However, changes in the flow and sedim ent inputs from upstream or tributaries hinder the adaptation. Also, the adaptation to capacity regime is size dependent, the finer the sediment size the slower the adaptation is, and vice versa. It is shown that the capacity model may entail considerable errors compared to the non-capacity model. For modelling of non-uniform bed load, non-capacity modelling is recommended, in which the temporal and spatial scales required for adaptation are explicitly appreciated.展开更多
Coupled flood and sediment transport modelling in large-scale domains has for long been hindered by the high computational cost.Adaptive mesh refinement is one of the viable ways to solving this problem without degrad...Coupled flood and sediment transport modelling in large-scale domains has for long been hindered by the high computational cost.Adaptive mesh refinement is one of the viable ways to solving this problem without degrading the accuracy.This goal can be accomplished through mesh adaptation,e.g.,mesh coarsening and refining based on the dynamic regime of the flow and sediment transport along with bed evolution.However,previous studies in this regard have been limited to cases either without involving sediment transport or featuring flow-sediment-bed decoupling and the assumption of sediment transport capacity,which are not generally justified.Here,a coupled hydrodynamic and non-capacity sediment transport model is developed on adaptive non-uniform rectangular mesh.The proposed model is validated against experimental tests and numerical results based on the fixed meshes.It is demonstrated that the proposed model can properly capture shock waves,resolve the wetting/drying transition and reproduce morphological evolution.Compared with models based on the fixed meshes,the proposed model features great advantage in computational efficiency and holds promise for wide applications.展开更多
基金funded by the N atural Science Foundation of China (G rants No. 11172217, 51279144 and 11432015)Chinese Academy of Sciences (G rant No. KZZDEW -05-01-03)
文摘Rivers often witness non-uniform bed load sedim ent transport. For a long tim e, non-uniform bed load transport has been assum ed to be at capacity regime determined exclusively by local flow. Yet whether the capacity assumption for non-uniform bed load transport is justified remains poorly understood. Here, the relative time scale of non-uniform bed load transport is evaluated and non-capacity and capacity models are compared for both aggradation and degradation cases with observed data. As characterized by its relative time scale, the adaptation of non-uniform bed load to capacity regime should be fulfilled quickly. However, changes in the flow and sedim ent inputs from upstream or tributaries hinder the adaptation. Also, the adaptation to capacity regime is size dependent, the finer the sediment size the slower the adaptation is, and vice versa. It is shown that the capacity model may entail considerable errors compared to the non-capacity model. For modelling of non-uniform bed load, non-capacity modelling is recommended, in which the temporal and spatial scales required for adaptation are explicitly appreciated.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172217,51279144&11432015)
文摘Coupled flood and sediment transport modelling in large-scale domains has for long been hindered by the high computational cost.Adaptive mesh refinement is one of the viable ways to solving this problem without degrading the accuracy.This goal can be accomplished through mesh adaptation,e.g.,mesh coarsening and refining based on the dynamic regime of the flow and sediment transport along with bed evolution.However,previous studies in this regard have been limited to cases either without involving sediment transport or featuring flow-sediment-bed decoupling and the assumption of sediment transport capacity,which are not generally justified.Here,a coupled hydrodynamic and non-capacity sediment transport model is developed on adaptive non-uniform rectangular mesh.The proposed model is validated against experimental tests and numerical results based on the fixed meshes.It is demonstrated that the proposed model can properly capture shock waves,resolve the wetting/drying transition and reproduce morphological evolution.Compared with models based on the fixed meshes,the proposed model features great advantage in computational efficiency and holds promise for wide applications.
