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Vertical sorting in collisional layer of bimodal sediment transport
Journal of Hydrology and Hydromechanics ( IF 1.9 ) Pub Date : 2020-03-01 , DOI: 10.2478/johh-2020-0003
Štěpán Zrostlík 1 , Václav Matoušek 1
Affiliation  

Abstract Intense collisional transport of bimodal sediment mixture in open-channel turbulent flow with water as carrying liquid is studied. The study focusses on steep inclined flows transporting solids of spherical shape and differing in either size or mass. A process of vertical sorting (segregation) of the two different solids fractions during the transport is analyzed and modelled. A segregation model is presented which is based on the kinetic theory of granular flows and builds on the Larcher-Jenkins segregation model for dry bimodal mixtures. Main modifications of the original model are the carrying medium (water instead of air) and a presence of a non-uniform distribution of sediment across the flow depth. Testing of the modified model reveals that the model is applicable to flow inclination slopes from 20 to 30 degrees approximately, making it appropriate for debris flow conditions. Changing the slope outside the specified range leads to numerical instability of the solution. A use of the bimodal mixture model is restricted to the grain size ratio 1.4 and no restriction is found for the grain mass ratio in a realistic range applicable to natural conditions. The model reveals trends in the vertical sorting under variable conditions showing that the sorting is more intense if flow is steeper and/or the difference in size or mass is bigger between the two sediment fractions in a bimodal mixture.

中文翻译:

双峰输沙碰撞层垂直分选

摘要 研究了以水为载液的明渠湍流中双峰沉积物混合物的强烈碰撞输运。该研究侧重于输送球形固体且大小或质量不同的陡峭倾斜流。对运输过程中两种不同固体部分的垂直分选(分离)过程进行了分析和建模。提出了一种分离模型,该模型基于颗粒流的动力学理论,并建立在干燥双峰混合物的 Larcher-Jenkins 分离模型之上。对原始模型的主要修改是携带介质(水而不是空气)以及在整个流动深度上存在不均匀分布的沉积物。对修正模型的测试表明,该模型适用于大约 20 到 30 度的流动倾斜坡度,使其适用于泥石流条件。在指定范围之外改变斜率会导致解的数值不稳定。双峰混合模型的使用仅限于晶粒尺寸比 1.4,并且在适用于自然条件的实际范围内没有发现对晶粒质量比的限制。该模型揭示了可变条件下垂直分选的趋势,表明如果流动更陡峭和/或双峰混合物中两种沉积物部分之间的尺寸或质量差异更大,则分选会更加强烈。4 并且在适用于自然条件的现实范围内没有发现对颗粒质量比的限制。该模型揭示了可变条件下垂直分选的趋势,表明如果流动更陡峭和/或双峰混合物中两种沉积物部分之间的尺寸或质量差异更大,则分选会更加强烈。4 并且在适用于自然条件的现实范围内没有发现对颗粒质量比的限制。该模型揭示了可变条件下垂直分选的趋势,表明如果流动更陡峭和/或双峰混合物中两种沉积物部分之间的尺寸或质量差异更大,则分选会更加强烈。
更新日期:2020-03-01
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