The Effects of Fluid-Particle and Particle-Particle Interactions on the Structure and Flow Properties of Suspensions of Fibers and Disks

流体-颗粒和颗粒-颗粒相互作用对纤维和圆盘悬浮液结构和流动性能的影响

• 批准号: 0332902
• 负责人: Donald Koch
• 金额: $ 27.95万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2008-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0332902&HistoricalAwards=false
• 关键词: Effects; Fluid; Particle; Interactions; Structure

AbstractCTS-0332902D. Koch, Cornell UniversityIntellectual Merit: A major challenge for the scientific understanding and engineering design of structured materials and complex fluids is to determine the effects of fluid flow on the structure and properties of non-spherical-particle suspensions. A balanced approach of analytical theory, computer simulation and experiment will be applied to two problems on the forefront of this topic: (a) The orientation of slender fibers in high Reynolds number laminar and turbulent flows; and (b) The effects of fluid-mediated particle-particle interactions on the structure and rheology of suspensions of disks. While detailed theoretical models and careful experimental measurements are available for the flow-induced structure in fiber suspensions in viscous fluids, relatively little is known about the rotation of fibers when fluid inertia is important on the fibers length scale. More generally, the proper description of particle-fluid interactions for particles whose size is comparable to or larger than the size of the smallest eddies of a turbulent flow constitutes the most important current challenge in the description of particle-laden turbulent flows. In the proposed project, a novel simulation method will be developed that couples a slender-body description of the force distribution along a fiber with a spectral solution of the Navier-Stokes equations to describe particle-fluid interactions in a turbulent flow when the fiber length is comparable with the size of the eddies of the turbulent flow and inertia influences the fluid velocity disturbances produced by the fiber. This model will be applied to predict the turbulence-induced dispersion of fiber positions and orientations and the rate of sedimentation of fibers in turbulent flows. The most basic question concerning the motion of fibers at finite Reynolds number is how a fiber will rotate in a moderate Reynolds number simple shear flow. In the PIs current NSF sponsored research, analytical predictions have been obtained indicating that inertial effects cause a fibers orientation to drift toward the vorticity axis of a simple shear flow. The proposed study includes an experimental investigation of the motion of single fibers in a Couette cell to validate the predictions for the direction and rate of migration of fiber orientation. The proposed project will also extend the experimental and analytical approaches used to study fluid-mediated fiber-fiber interactions to understand the nature of such interactions in materials filled with disk-shaped particles. Microlithography methods will be used to produce model systems of rigid disks suitable for studies of the rheology and flow-induced orientation of disks in Newtonian fluids over a range of particle concentrations. This experimental study will be complemented by a theoretical analysis of disk-disk interactions to predict the effects of hydrodynamic interactions on the orientation distribution and rheology of the disk suspensions. Broader Impacts: High-aspect ratio fibers and disks are commonly used to enhance the mechanical, thermal and electrical properties of polymeric materials. These properties are highly sensitive to the structure induced by fluid flow when the materials are processed in the molten state. At the present time, commercial software based on the rotation of fibers in a low Reynolds number Newtonian fluid with a rotary diffusion to describe fiber-fiber interactions is widely used to predict structure in fiber composites. The experimental and theoretical studies of the effects of disk-disk interactions on disk orientation will provide the first step toward developing engineering models for the flow-induced structure in polymeric materials filled with platelet shaped particles such as mica flakes and silica clay particles. During the production of paper, pulp fibers suspended in water flow onto a porous conveyer belt to form a fiber network. It is desirable to use a turbulent fluid flow to disperse the fibers uniformly in space with isotropic orientations. In these flows, the Reynolds number based on the fiber length is O (10). The simulation method developed in this project will provide the first rigorous description of fiber motion under these conditions. The project will train a doctoral student and undergraduate researchers with the ability to interface analytical approaches with computer simulation and validate their models experimentally.

摘要CTS-0332902 D。Koch，Cornell University知识专长：对结构材料和复杂流体的科学理解和工程设计的一个主要挑战是确定流体流动对非球形颗粒悬浮液的结构和性质的影响。 一个平衡的分析理论，计算机模拟和实验的方法将适用于两个问题的前沿这一主题：（a）在高雷诺数层流和湍流中的细长纤维的取向;和（B）流体介导的颗粒-颗粒相互作用的结构和流变性的磁盘悬浮液。 虽然详细的理论模型和仔细的实验测量可用于在纤维悬浮液中的粘性流体的流动诱导结构，相对较少的是已知的纤维的旋转时，流体惯性是重要的纤维长度尺度。 更一般地说，适当的描述颗粒的颗粒-流体相互作用的大小是可比的或大于湍流的最小涡流的大小构成了当前最重要的挑战，在描述的颗粒负载的湍流。 在拟议的项目中，将开发一种新的模拟方法，耦合细长体描述的力分布沿着的纤维与频谱解决方案的Navier-Stokes方程描述颗粒-流体相互作用时，纤维长度是可比的湍流的涡流的大小和惯性的影响，由纤维产生的流体速度扰动。 该模型将被应用于预测湍流诱导的纤维位置和取向的分散和纤维在湍流中的沉降速率。 有限雷诺数下纤维运动的最基本问题是纤维在中等雷诺数的简单剪切流中如何旋转。 在美国国家科学基金会赞助的研究中，已经获得了分析预测，表明惯性效应导致纤维取向向简单剪切流的涡度轴漂移。 建议的研究包括一个实验调查的单纤维在库埃特细胞的运动，以验证预测的方向和速度的迁移的纤维取向。 拟议的项目还将扩展用于研究流体介导的纤维-纤维相互作用的实验和分析方法，以了解填充有盘形颗粒的材料中这种相互作用的性质。 微光刻方法将用于生产模型系统的刚性磁盘适用于研究的流变学和流动诱导的取向的磁盘在牛顿流体中的颗粒浓度的范围。 本实验研究将补充的理论分析的磁盘-磁盘的相互作用，以预测流体动力学相互作用的磁盘悬浮液的取向分布和流变学的影响。更广泛的影响：高纵横比纤维和圆盘通常用于增强聚合物材料的机械、热和电性能。 当材料在熔融状态下加工时，这些性质对由流体流动引起的结构高度敏感。 目前，商业软件的基础上旋转的纤维在低雷诺数牛顿流体与旋转扩散来描述纤维-纤维相互作用被广泛用于预测纤维复合材料的结构。 盘-盘相互作用对盘取向的影响的实验和理论研究将为开发填充有片状颗粒（如云母片和二氧化硅粘土颗粒）的聚合物材料中的流动诱导结构的工程模型提供第一步。 在造纸过程中，悬浮在水中的纸浆纤维流到多孔传送带上形成纤维网络。 希望使用湍流流体流以各向同性取向将纤维均匀地分散在空间中。 在这些流动中，基于纤维长度的雷诺数为O（10）。 在这个项目中开发的模拟方法将提供在这些条件下的纤维运动的第一个严格的描述。 该项目将培养一名博士生和本科生研究人员，使他们能够将分析方法与计算机模拟相结合，并通过实验验证他们的模型。