Presidential Young Investigator Award: Dynamic Properties of Concentrated Suspensions (REU Supplement)

叙述：使用非胶体的浓缩悬浮液 粒子在不同的应用，如血液流动， 动脉和人造器官以及煤-油混合泥浆的 燃料炉使详细了解他们的性质 势在必行 这些行为表现出的几个方面 目前人们对悬浮液的种类还知之甚少， 研究了 休克引起的移位： 已经表明，当非- 胶体颗粒受到剪切， 由于浓度梯度而产生的流线。 机制 作为对这种迁移的解释， 诱导迁移也可以由剪切应力的梯度引起。 初步的实验为这一来源提供了间接证据。 粒子漂移;然而，迄今为止的结果还远远没有 结论性的 旨在证明或反驳 剪切应力梯度引起的迁移的存在， 正在进行。 表面粗糙度对悬浮液流变性的影响： 最近的研究表明，集中的行为 非胶体颗粒的悬浮严重依赖于 颗粒的表面性质。 这主要是由于 悬浮液中颗粒表面的接近程度 经受剪切。 初步分析显示， 这些悬浮液表现出显著的非牛顿性质 由于存在小程度的表面粗糙度 这些粒子。 通过实验和数值模拟， 它试图量化表面之间的关系， 粗糙度和浓缩液的流变特性 停职 浓悬浮液中的流动诱导微观结构： 悬浮液的微观结构在 确定重要的流变性能。 很大进展 在确定稀体系的微观结构时， 对于浓悬浮液，仍然知之甚少。 一个关键 一个尚未回答的问题是，粒子在多大程度上 在非胶体颗粒的浓缩悬浮液中聚集。 数值模拟表明， 相互作用的粒子可能导致形成大的结构 在浓缩的悬浮液中;然而， 应该是颗粒表面性质的强函数， 大骨料的存在尚待证实 实验性的 利用一种新的实验技术， 试图通过测量两者来确定聚集程度， 颗粒分布函数和颗粒速度 非胶体球的浓悬浮液的分布 经历简单的剪切流动。 最终，这项研究将 扩展到包括微观结构的完整测定 作为流动几何形状的函数， 颗粒表面性质，如表面粗糙度，和颗粒 形状

Narrative: The use of concentrated suspensions of non-colloidal particles in such diverse applications as the flow of blood in arteries and artificial organs and of coal-oil slurries in mixed fuel furnaces makes the detailed understanding of their properties imperative. Several aspects of the behavior exhibited by these types of suspensions which are, as yet, poorly understood are being investigated. SHEAR INDUCED MIGRATION: It has been shown that when concentrated suspensions of non- colloidal particles are sheared, the particles will drift across streamlines due to gradients in concentration. The mechanism proposed as an explanation for this migration suggests that shear induced migration may arise from gradients in shear stress as well. Preliminary experiments provide indirect evidence for this source of particle drift; however, the results to date are far from conclusive. Experiments aimed at proving or disproving the existence of migrations arising from gradients in shear stress are being conducted. THE EFFECT OF SURFACE ROUGHNESS ON SUSPENSION RHEOLOGY: Recent work has demonstrated that the behavior of a concentrated suspension of non-colloidal particles is critically dependent on the surface properties of the particles. This is primarily due to the closeness of the approach of the particle surfaces in a suspension undergoing shear. Preliminary analysis suggests that the most significant non-Newtonian properties manifested by these suspensions result from the presence of a small degree of surface roughness on these particles. Using both experimental and numerical simulation, it is being attempted to quantify the relationship between surface roughness and the rheological properties of concentrated suspensions. FLOW INDUCED MICROSTRUCTURE IN CONCENTRATED SUSPENSIONS: The microstructure of a suspension plays a critical role in determining important rheological properties. While much progress has been made in determining the microstructure in dilute systems, for concentrated suspensions it remains poorly understood. A key question that is as yet unanswered is the degree to which particles aggregate in concentrated suspensions of non-colloidal particles. Numerical simulations suggest that the lubrication forces between interacting particles may lead to the formation of large structures in concentrated suspensions; however, the formation of aggregates should be a strong function of particle surface properties and the existence of large aggregates has yet to be confirmed experimentally. Using a novel experimental technique, it is being attempted to determine the degree of aggregation by measuring both the particle distribution function and particle velocity distribution of a concentrated suspension of non-colloidal spheres undergoing simple shear flow. Eventually, this study will be expanded to include the complete determination of the microstructure of concentrated suspensions as a function of the flow geometry, particle surface properties such as surface roughness, and particle shape.