层流区Shields曲线分布规律试验  

Experimental study of distribution law of shields curve in laminar regime

作　　者：洪安宇[1,2] 王正中[1] 赵延风[1] 

机构地区：[1]西北农林科技大学水利与建筑工程学院,陕西杨凌712100 [2]Department of Physics,Clark University

出　　处：《水科学进展》2015年第6期837-845,共9页Advances in Water Science

基　　金：国家自然科学基金资助项目(51279168);"十二五"国家科技支撑计划资助项目(2012BAD10B02)~~

摘　　要：为探明层流条件下Shields曲线的分布规律,运用电荷耦合组件(Charge Coupled Device,CCD)成像技术结合激光扫描及计算机图像处理技术,在水和甘油混合液中对无黏性均匀玻璃颗粒的起动拖曳力进行测量,并根据层流绕流理论建立了无黏性均匀颗粒的滚动起动模型,提出层流条件下无黏性均匀颗粒的量纲一起动拖曳力公式。试验观测发现在层流范围内希尔兹数呈规则的带状分布,流体作用引起颗粒床表面粗化并导致床面颗粒突起减小,使颗粒起动拖曳力增大1倍以上。结果表明颗粒床表面结构性状直接影响着颗粒起动拖曳力的大小,在层流区Shields曲线具有带状分布特性。In order to study the distribution law of Shields curve in laminar regime,the critical tractive force for the onset motion of uniform non-cohesive glass beads is investigated based on the CCD（ charge coupled device） imaging technology combined with laser scanning and computer image processing technology,using a mixture of water and glycerol. According to the laminar flow theory,the rolling model for the onset motion of non-cohesive particles is established and an equation for non-dimensional critical tractive force is derived. Experiments show that the particle Reynolds number versus Shields number is a systematic band distribution in the laminar region; further,fluid flow induces bed armoring and leads to the decrease in particle protrusion on the granular surface,the critical tractive force can be doubled consequently. This indicates that the structure of the granular surface has a significant impact on the critical tractive force for the onset motion of particles,and band distribution is a characteristic of Shields curve in the laminar regime.

关 键 词：Shields曲线 层流 CCD成像技术 无黏性均匀颗粒 颗粒床表面结构 

分 类 号：TV142[水利工程—水力学及河流动力学]