Study on non-equilibrium sediment transport in the sandy river erosion
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摘要: 通过动床水槽试验,观测沙波运动,揭示了湍流扫荡河床使表层床沙产生频发的群体起动冲刷现象。据此,提出了床沙交换及冲刷粗化分二个层次的物理模式;分析了冲刷时表层床沙粗化的必然性,确定了悬移质扩散过程中适于非均匀沙河床的新的近底边界条件。依据所建立的不平衡输沙立面二维数学模型,计算了大量不同情况下的含沙量扩散恢复过程,据此总结出了冲刷时含沙量恢复饱和系数α的预报公式及变化规律。Abstract: The flume experiments on the mobile sand bed are made in this paper.The frequent group initiation of bed material is found to occur by the turbulent sweep.The sand-wave movement is also observed.According,two physical models of the bed material exchange in different levels are presented to prove the coarsening of surface bed material makes the recovering distance much longer than that for the condition of uniform bed material,and thus greatly effects the non-equilibrium sediment transport process.The new boundary condition considering the coarsening of the surface non-uniform bed material is obtained.Lots of non-equilibrium sediment transport process in different hydraulic and bed material conditions are calculated by the new lognitudinal-vertical 2-D mathematical model of non-equilibrium sediment transport considering the coarsening of surface bed materiel.Finally,the experiential expression of the recovering coefficient of sediment concentration is discussed.
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Keywords:
- sandy river /
- river erosion /
- non-equilibrium sediment transport /
- mechanism
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