冲淤面积分配模式对黄河下游一维模型计算结果的影响

冲淤面积分配模式是一维水沙数学模型中需要处理的技术问题之一,合理选择冲淤面积分配模式能够保证一维模型的计算精度。本文首先建立了用于模拟实际游荡型河流复杂断面形态下洪水演进的一维水沙耦合模型。然后以黄河下游游荡型河段为研究对象,利用下游1992年实测高含沙洪水过程资料对所建模型进行了验证,计算值与实测值吻合较好。最后采用一维模型中常用的五种冲淤面积分配模式计算了该场次高含沙洪水过程,分析了不同分配模式对模拟结果的影响。结果表明:等厚度分配模式的计算效果相对较好,按子断面流量分配与按挟沙力分配两种模式的计算精度相当。冲淤面积分配模式对流量及水位影响相对较小,而对含沙量及河道冲淤过程影响较为明显,尤其对于淤积严重的河段。

Influence of cross section area distribution modes of erosion and deposition to results of one-dimensional morphodynamic model for the Lower Yellow River

The distribution mode of erosion and deposition area is one of technical issues in one-dimensional (1-D) morphodynamic models,and a reasonable distribution mode can ensure the calculation precision of 1-D model.In the current study,a coupled morphodynamic model was first developed,which can predict flood routing in the braided river with complex cross-sectional geometry.The braided reach of the Lower Yellow River (LYR) was chosen as a study object,and the model was then validated by the measurements of the 1992 flood event,and close agreement was obtained between the model predictions and the observed data.In addition,the validate model was used to simulate the same flood event occurring in the LYR using different distribution modes of erosion and deposition area,and the effect of different distribution modes on the modelling results was investigated.The results show that the mode of equal thickness distribution is relatively better,and the calculation precisions of sub-sectional flow discharge distribution and sediment transport capacity distribution are equivalent.It is also found that different area distribution modes can influence the predicative accuracy of the proposed model;the effects on the simulated discharges and water levels are relatively lower,as compared with the effect on the concentrations and channel evolution volumes,especially for the reach undergoing severe deposition.