均匀切变水流对黏性细颗粒泥沙絮凝的影响研究  

The effect of uniform shear flow on flocculation of cohesive fine sediment

作　　者：柴朝晖[1] 杨国录[1,2] 陈萌[1] 余明辉[1] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,湖北武汉430072 [2]武汉大学-宇星公司水利环境工程技术研究中心,湖北武汉430072

出　　处：《水利学报》2012年第10期1194-1201,共8页Journal of Hydraulic Engineering

基　　金：国家重点基础科学研究(973)计划资助项目(2011CB403300);国家自然科学基金项目(11072180);中央高校基本科研业务费专项资金资助(2012206020202)

摘　　要：黏性细颗粒泥沙的絮凝是河流动力学中一个重要且尚未完善的研究课题。本文以分形聚集生长理论为基础,考虑了絮团破碎、泥沙浓度等因素的影响,使用三维无网格方法,在MATLAB平台上通过模拟泥沙颗粒和絮团在布朗运动、重力沉降和均匀切变水流作用下的碰撞黏结过程,研究了水流剪切作用对黏性细颗粒泥沙絮凝的影响。研究结果表明:水流作用可提高颗粒之间的碰撞几率,促进絮凝,但高水流剪切力作用下絮团破碎现象明显,因此,水流速度梯度的大小对细颗粒泥沙的絮凝有一定的影响,即絮凝速度及絮团平均粒径随水流流速梯度的增大呈先增后减的规律;均匀切变水流作用下,絮团粒径分布均匀化,絮团在垂直水流方向上发育较好且分形维数较大。本文研究成果是进一步研究天然河道中黏性细颗粒泥沙絮凝机理的成功尝试。Flocculation of cohesive fine sediment is an important research subject in river dynamics but not perfect.Based on fractal cluster growing theory,the effect of uniform shear flow on the flocculation of cohesive fine sediment was studied through simulating the process of collision and bonding of particles and clusters under the effect of brown motion,gravity settling and uniform shear flow in MATLAB using 3-D off-lattice algorithm,considering the breakage of flocs as well as the effect of sediment concentration on viscosity of suspension.The results reveal that flow force can promote the flocculation of cohesive fine sediment by improving the collision probability of particles,while the breakage of flocs becomes significant under high flow shear force,so the velocity gradient affects the flocculation process to a certain extent,that is,the flocculation rate and the average diameter of flocs appear the trend from increasing to decreasing as the velocity gradient increased;the size distribution of flocs becomes more uniform,flocs have a better development in the vertical direction of flow and fractal dimension of flocs is high under the action of uniform shear flow.It is a successful attempt for further study of flocculation mechanism of cohesive fine sediment in natural river.

关 键 词：黏性细颗粒泥沙 均匀切变水流 三维模拟 速度梯度 分形维数 

分 类 号：TV149.2[水利工程—水力学及河流动力学]