【作者】 孙光明；

【导师】 邵雪明；

【作者基本信息】 浙江大学 ， 流体机械及工程， 2006， 硕士

【摘要】 粒子流悬浮流在自然界和工业应用中普遍存在，例如在化学和石油工业中就经常应用不同粒子在沉降行为上的差异来实现粒子和流体，以及不同尺度和性质粒子之间的分离。近十多年来，一些针对粒子流的直接数值模拟方法得到了的很大的发展，因为直接数值模拟方法能比较准确地同时给出悬浮流的微观和宏观的信息，因此已成为研究粒子悬浮流的一种重要手段。基于分布式拉格朗日乘子的虚拟区域方法(DLM/FD)是近年来出现的直接数值模拟粒子流的新方法之一。其基本思想是：通过假设流体也充满粒子占据的空间，这样把一个几何复杂区域内的问题扩展到一个相对大的，但几何简单的区域中，控制流体流动的N-S方程和控制粒子运动的刚体运动方程通过无滑移边界条件和作用在粒子上的力和力矩耦合在一起进行求解，而刚体运动的限制则通过一个拉格朗日乘子来施加。这样在计算时不但作用在粒子上的力和力矩不需要再显式计算，同时也可以应用固定的结构化网格和快速求解算法，避免了计算过程中重新更新和划分网格的需要。 本文对基于分布式拉格朗日乘子的虚拟区域方法作了详细介绍，并在求解算法上进行了一定的改进，即采用基于半交错网格的有限差分方法来求解流体流动子问题，从而大大提高了计算效率。采用基于分布式拉格朗日乘子的虚拟区域方法，本文对单个、两个圆球粒子在垂直方槽中的沉降过程进行了三维数值模拟，分析了不同雷诺数下单个圆球粒子的沉降轨迹、沉降速度的变化和相应的尾涡结构，也给出了两个圆球粒子之间的DKT过程。本文还设计了圆球粒子在垂直方槽中沉降的实验装置，对圆球粒子的沉降特性进行了实验研究，并且对数值模拟结果进行了验证，实验结果和数值模拟结果吻合较好。更多还原

【Abstract】 Particulate flows are commonly encountered in various natural phenomena and industrial processes, such as in the chemical and petroleum industries, the sedimentation of particles is a way of separating particles from fluid, as well as a way separating particles with different settling speeds from each other. In last decades, a variety of direct numerical simulation (DNS) methods for the particulate flows have been developed. DNS is capable of providing both microscopic and macroscopic information of the particulate flows and consequently has become an important investigative tool for multiphase flow problems. Distributed Lagrange multiplier/fictitious domain (DLM/FD) method is a promising new DNS method for the particulate flows. The basic idea of DLM/FD method is to imagine that interior space of the solid is filled with the same fluids as outside, and the fluids inside, and on solid boundary is constrained to move at the same velocity of the solid by using a distributed Lagrange multiplier. Thus a problem on a geometrically complex domain can be extended to a larger, simpler domain, which allows a fixed structured mesh can be used for the entire computation, and eliminates the need for repeated remeshing and projection.In this paper, the DLM/FD method was introduced and a new implementation of DLM/FD method is presented by using a half-staggered finite-difference scheme for the fluid flow sub-problem. Based on the new implementation, the efficiency of DLM/FD method is improved significantly. Then the DLM/FD method was used to simulate the sedimentations of a single spherical particle and two spherical particles in a vertical channel. The sedimenting behavior including trajectory, velocity and wake was analyzed at different Reynolds numbers. The DKT interaction between two spherical particles was presented. In addition, experimental research on the sedimentation of spherical particle was also performed. The comparison shows that simulation results agree well with experimental results.更多还原