Improved estimation of critical bed shear stress downstream of low-head weirs in streams with coarse bed material  

作　　者：Anbin Li Bruce W.Melville Yifan Yang Liyao Gao Asaad Y.Shamseldin Genguang Zhang 

机构地区：[1]Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas,Ministry of Education,Northwest Agriculture&Forestry University,Yangling,China [2]Department of Civil and Environmental Engineering,The University of Auckland,Auckland,New Zealand [3]State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan,China

出　　处：《International Journal of Sediment Research》2024年第3期340-354,共15页国际泥沙研究（英文版）

基　　金：the China Scholarship Council(CSC)(202206300069)for the financial support of this research and to thank the University of Auckland for providing office space and facilities for the current research;the National Natural Science Foundation of China(Grant Nos.51879227,51279170);the Key Research and Development Projects of Shaanxi Province(Grant No.007214172043)are gratefully acknowledged.

摘　　要：Existing methods for estimating critical bed shear stress are limited and usually do not consider local scour processes;therefore,the accuracy of numerical modeling is usually compromised.This paper presents the results of physical experiments on scour downstream of low-head weirs and proposes new equations for estimating the critical bed shear stress in scour holes.The experiments were done using a camel hump weir and coarse-bed materials which are applicable to steep streams with coarse-bed materials(gravel,rocks,etc.).The critical shear stress was regarded as the bed shear stress within the scour holes,which was determined using the three-dimensional(3D)flow field and bed morphology measured at the equilibrium scour state.The influence of the sediment size also was investigated.The experimental results showed that a scour hole can be divided into three zones:Zone-Ⅰ for the upstream scour slope,Zone-Ⅱ for the downstream scour slope,and Zone-Ⅲ for the downstream slope of the sediment deposit downstream of the hole.The relation between the critical shear stress of the bed surface in Zone-Ⅰ,the flow rate,and bed position was established,and the new equations yielded better accuracy than existing methods.In addition,the relation between the critical shear stress and the slope of the bed and the ratio of the local water depth to the particle size in Zone-Ⅱ and Zone-Ⅲ were established.After verification,the calculation results of the newly proposed equations were in good agreement with the standard values of the dimensionless critical Shields parameter obtained through processing the experimental results in the current study.Further discussion is provided regarding the integration of the parameters calculated applying the new parameters in the numerical models.

关 键 词：Coarse bed material Low-head weirs Local scour Critical bed shear stress Numerical models 

分 类 号：TV14[水利工程—水力学及河流动力学]