【作者】 张志雁；

【导师】 牧振伟；

【作者基本信息】 新疆农业大学 ， 水力学及河流动力学， 2011， 硕士

【摘要】 地转科氏力对大尺度水域水流运动的影响比较明显,在小尺度流体运动过程中一般把地转科氏力忽略不计,而对小尺度旋转多相流中固体颗粒是否受到旋转科氏力的影响,国内外的研究很少。本文采用试验研究和数值模拟方法对垂直放置与水平放置螺旋管道内球形单颗粒运动特性进行分析。试验过程中使用高速摄像机捕捉颗粒运动轨迹以获取其运动参数,采用单颗粒动力学模型分析颗粒在旋转流中的运动特性和受力规律。数值模拟过程中采用RNGκ-ε模型以及加载基于C语言的UDF文件的动网格技术,对二维垂直放置的螺旋管道内颗粒运动进行研究。得到以下主要结论：(1)垂直放置的螺旋管道在同一流量下,单颗粒无论在上升还是下降过程中,所受旋转科氏力、离心力和阻力随着管轴半径的减小而增大。颗粒在整运动过程中所受离心力随流量的增大或管轴半径的减小而增大,而且离心力的量值在整个过程中占据了重要作用。阻力和旋转科氏力在量值上具有同步性,而且两者量值上相差不大。重力对颗粒有较大的影响作用。速度无量纲量λ(颗粒切向速度与水流速度之比)与力的无量纲量ζ(旋转科氏力与离心力之比)存在明显的指数关系。颗粒所受旋转科氏力可以忽略的情况出现次数相对较少,约占实测总样本的四分之一(2)垂直放置的螺旋管道内作悬浮旋转运动的单颗粒,在整个运动过程中,主要受到有效重力、阻力的作用,在径向分量上主要受到旋转科氏力和有效重力的作用。在一定条件下,旋转科氏力与离心力满足抛物线的关系。绝大多数情况下,颗粒所受旋转科氏力为离心力的2～3个数量级。(3)水平放置的螺旋管道内作运动的单颗粒,主要受到离心力、阻力和旋转科氏力作用,但阻力径向分量作用较小。在同一管轴半径下,阻力随流量的增大而减小,旋转科氏力和离心力则随流量的增大而增大。在同一流量下,颗粒所受离心力随管轴半径的减小而增大,而旋转科氏力变化较为复杂,但总体而言,随管轴半径的减小而增大。无量纲量λ与ζ存在明显的指数关系。颗粒所受旋转科氏力不能忽略的样本数约占实测总样本数的四分之三。(4)采用动网格技术控制单颗粒运动轨迹的方法,对垂直放置螺旋管道内颗粒进行二维数值模拟,结果表明：在上升过程中,颗粒主要受到阻力、有效重力和旋转科氏力作用,而离心力与虚假质量力则较小。与实测数据相比,旋转科氏力的量值偏大,而离心力和阻力的量值偏小。在下降过程中,颗粒主要受到阻力、有效重力、离心力及旋转科氏力的作用,而虚假质量力则较小。与实测数据相比,而离心力和旋转科氏力的量值比较接近,但阻力比实测数据偏大,阻力径向分量偏大较明显。数值模拟能够较准确地反映颗粒的运动过程,数值模拟结果与试验数据比较吻合。无论是在垂直放置与水平放置的螺旋管道的模型试验,还是数值模拟过程中,颗粒所受旋转科氏力作用均占较大比例,即在小尺度低速度旋转流中,在受力分析中旋转科氏力不应被忽略。更多还原

【Abstract】 Coriolis effect is obviously of water movement in large-scale water-area, and in small-scale flow, Coriolis force can be negligible, but there is little research for rotational Coriolis force in small-scale rotational multiphase flow in home and abroad. In this thesis, experiments and numerical simulation are done in vertical and horizontal spiral duct to study motion characteristics and force analysis of spherical single particle. In experiment, works are done by catching particle trajectory using high-speed camera and employing kinetic model of single granular. In numerically simulation, the RNGκ-εmethod and dynamic mesh method loaded UDF file based C language are employed to simulate a single particle trajectory in two-dimensional vertical spiral duct. The major conclusions are as following.(1) In vertical spiral duct, at the same flow, both in rising movement and in decline movement, rotational Coriolis force, centrifugal force and drag force upon single particle increase with pipe radius decrease. In whole movement, centrifugal force upon particle increases with the flow increase or with the pipe radius decrease, and the value of centrifugal force is an important role. The value of rotational Coriolis force sync with drag force, and both value are similar. Effectual gravity upon a particle is important in the whole movement. There is exponential relation between dimensionless quantityλandζ. The samples number of rotational Coriolis force which can be ignored measured measured about one-quarters of the total.(2) In the whole movement of a single particle suspended in vertical spiral duct, effective gravity, rotational Coriolis force and drag force are mainly effect upon the single particle, but in radial component, the main force are rotational Coriolis force and effective gravity, others are small. On some conditions, there is parabolic relation of rotational Coriolis force to centrifugal force. Rotational Coriolis force upon single particle is larger than centrifugal force 2 to 3 orders of magnitude in most conditions.(3) In horizontal spiral duct, centrifugal force, rotational Coriolis force and drag force are mainly effect upon the single particle, but the radial component of drag force is very small. At the same pipe radius, drag force decreases with flow increase, while rotational Coriolis force and centrifugal force increases with flow increase. At the same flow, centrifugal force upon particles decreases with pipe radius increase, while the changes of rotational Coriolis force is complicated, but it increase with pipe radius increasing in most codition. There is exponential relation between dimensionless quantityλandζ. The sample number of rotational Coriolis force which can not be ignored measured about three-quarters of the total.(4) The dynamic mesh method is employed to numerically simulate a single particle trajectory in two-dimensional vertical spiral duct. The results show that:In rising movement, effective gravity and Coriolis force rotation are mainly effect upon the single particle, while centrifugal force and virtual mass force are small. Compared with the measured data, the magnitude of rotational Coriolis force is larger, while centrifugal force and drag force are smaller. In decline movement, effective gravity, centrifugal force and rotational Coriolis force are mainly effect upon the single particle, while virtual mass force is small. Compared with the measured data, the magnitude of centrifugal force and rotational Coriolis force are close to, but drag force is larger than the measured data, especially in the radial component of drag force. The simulation can reflex the movement of particle in the experiment, and the results agree with experiment data of forces.Therefore, both in experiments which were done in vertically or horizontal spiral duct and in numerical simulation, the proportion of rotational Coriolis force upon the single particle is major, that is, the rotational Coriolis force should not be ignored on force analysis of a particle in a small-scale low-velocity rotational two-phase flow.更多还原