搅拌槽内固体颗粒初始运动特性的实验研究与数值模拟

发布时间：2018-06-05 05:37

本文选题：搅拌槽 + 规则床层　；参考：《北京化工大学》2017年硕士论文

【摘要】：颗粒的初始运动广泛存在于自然界,例如河床沉积物的转移、颗粒床侵蚀、沙丘的形成,是研究河流泥沙输运及搅拌槽内固体颗粒悬浮初始阶段等涉及颗粒输运模型课题的理论基础。近些年来,有较多的学者研究了层流剪切流条件下的初始运动。本文将在前人的基础上继续探讨层流条件下颗粒的初始运动特性。本论文研究了方形搅拌槽内单颗粒在规则基板上的初始运动特性,搅拌桨为RT桨,基板由等大颗粒以三角形紧密排列的方式组成。实验后期通过Matlab程序获得了颗粒的运动轨迹和运动速度等相关信息。另外,本论文结合LBM方法对实验操作条件进行了直接数值模拟,获得了颗粒的运动轨迹、受力情况以及周围流场的详细信息。结果表明:(1)颗粒在基板上的运动以滚动状态为主,约占76%左右,并且颗粒沿着基板缝隙运动,很少跨过基板颗粒顶部;(2)临界初始运动转速随着颗粒密度的增大而增大,当颗粒密度比为2.26～3.36时,运动轨迹一致。当密度比为7.98～11.49时,运动轨迹与前者不同,为另一种形式;(3)颗粒直径会改变掩埋度,当颗粒与基板颗粒的直径比dp/ds0.5时,掩埋度明显增大,颗粒起动困难,所需的临界初始运动转速高;(4)当颗粒的初始位置.v/T的值相同时,尽管流型不同,但是不同x/T对应的临界Shields数的分布仍然关于y轴对称;(5)基于LBM模拟,临界悬浮转速的模拟值与实验误差约为3%,颗粒运动轨迹的模拟值和实验数据吻合很好;(6)当Re30时,颗粒在基板上运动主要受流体水平力的作用,流体水平力的贡献约占75%,其次是流体的矩的作用,约占25%,而升力可以忽略。
[Abstract]:The initial movement of particles is widespread in nature, such as river bed sediment transfer, particle bed erosion, sand dune formation, It is the theoretical basis for the research of sediment transport in rivers and the initial stage of solid particle suspension in stirred tank. In recent years, many scholars have studied the initial motion of laminar shear flow. This paper will continue to study the initial motion characteristics of particles in laminar flow on the basis of previous studies. In this paper, the initial motion characteristics of a single particle on a regular substrate in a square stirred tank are studied. The propeller is RT paddle, and the substrate is composed of the same size particles arranged in a triangle. In the later stage of the experiment, the movement track and velocity of particles were obtained by Matlab program. In addition, in this paper, the experimental operating conditions are directly simulated with the LBM method, and the moving trajectory, the force situation and the detailed information of the surrounding flow field are obtained. The results show that the motion of the particles on the substrate is mainly in the rolling state, accounting for about 76%, and the particles move along the slit of the substrate and rarely cross the top of the substrate.) the critical initial rotational speed increases with the increase of the particle density. When the particle density ratio is 2.26 ~ 3.36, the motion trajectory is the same. When the density ratio is 7.98 ~ 11.49, the moving trajectory is different from the former, and the particle diameter will change the burying degree. When the diameter ratio of the particle to the substrate particle is dp/ds0.5, the burying degree is obviously increased, and the particle starting is difficult. When the initial position of particles. V / T is the same, although the flow patterns are different, the distribution of critical Shields numbers corresponding to different x / T is still about y axisymmetric F5) based on LBM simulation. The simulated value of the critical suspension speed is about 3 with the experimental error, and the simulated value of the particle trajectory is in good agreement with the experimental data. (6) when Re30, the particle motion on the substrate is mainly affected by the horizontal force of the fluid. The contribution of horizontal force to fluid is about 75 percent, followed by the effect of fluid moment, about 25 percent, and the lift force can be neglected.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ027.2

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