RUI: Flow and Rheology of Particle-Fluid Suspensions with Variable Hydrophobicity

[67598]颗粒和颗粒流体体系的流变学是当前的重要研究方向。虽然许多研究集中在颗粒-流体混合物的干扰和流动上，但很少有研究表面化学的影响，例如颗粒的相对疏水性或亲水性。除了与土壤力学和工业问题（如对侵蚀、水径流和过滤的影响）中的表面化学相关外，疏水性还为颗粒的有效粘聚提供了一个控制参数。最近，干扰相图在具有吸引相互作用的胶体体系中的应用是由表面性质介导的颗粒-颗粒相互作用的重要性的相关例子。本研究旨在系统地研究疏水相互作用对具有良好特征的旋转鼓几何形状和通过收缩流中的阻塞行为的影响。研究了系统的流变学和动力学(i)随疏水颗粒的分数而变化，（ii）浸泡在不同极性的溶剂中以调整表面化学效应的重要性。这组实验与影响土壤/水相互作用的土壤颗粒的表面化学直接相关。此外，这些样品可以浸泡在不同极性的流体中，以控制表面化学效应的相对重要性。初步数据表明，疏水颗粒有很强的从水中分离的倾向，而当浸没在异丙醇或己烷等相对非极性的液体中时，反应减弱。将使用与胶体稳定性相关的已知颗粒/溶剂系统，然后将其扩展到不同极性的混相流体，这将允许对疏水颗粒之间的有效内聚进行微调控制。我们将定量测量有效疏水性，并将其与休止角、堵塞概率、偏析效应和流变剪切强度等流动特性相关联。与本提案的更广泛影响相关的最终目标是在高度跨学科的研究环境中对本科生进行科学培训。该项目将直接涉及在项目期间培训多达六名本科研究人员，但预计多达十名研究人员可能会受到影响，包括学年期间未支付的研究学分。此外，我们计划在二年级暑期聘请一名高中教师，以继续JMU培养教师的使命之一。学生将接触到材料科学和复杂系统的问题，包括流变学、动力学和图像处理。该计划的参与者将参与与JMU化学和材料科学本科生NSF研究经验（REU）相关的活动，与JMU化学和材料科学的其他60多名暑期本科生研究人员一起成为“学者社区”的一部分。总而言之，该项目有助于广泛影响从高中到研究生阶段的未来科学家队伍，让学生接受多相流前沿研究方面的培训。

1067598PI: UtterThe rheology of granular and granular-fluid systems is of significant current interest. While many studies focus on the jamming and flow of particle-fluid mixtures, there has been little work on the effects of surface chemistry, such as the relative hydrophobic or hydrophilic properties of the grains. In addition to the relevance of surface chemistry in soil mechanics and industrial problems, such as effects on erosion, water runoff, and filtration, hydrophobicity also provides a control parameter on the effective cohesion of grains. Recent applications of the jamming phase picture to colloidal systems with attractive interactions are related examples of the importance of grain-grain interactions mediated by surface properties. This Research at Undergraduate Institutions (RUI) proposal aims to systematically study the effect of the hydrophobic interactions in both the well-characterized rotating drum geometry and jamming behavior in flow through a constriction. Rheology and dynamics are studied in systems (i) that vary by fraction of hydrophobic grains and (ii) that are submerged in solvents of different polarities to tune the importance of the surface chemistry effects. This set of experiments has direct relevance to surface chemistry of soil particulates that impact soil/water interactions. In addition, these samples can be submerged in fluids of different polarity to control the relative importance of the surface chemistry effects. The preliminary data show both a strong tendency of hydrophobic grains to segregate from water and a decreased response when submerged in a relatively non-polar liquid like isopropanol or hexane. Known particle/solvent systems relevant to work on colloidal stability will be used and then extended to miscible fluids of different polarities which will allow fine-tuned control of the effective cohesion between hydrophobic grains. We will quantitatively measure the effective hydrophobicity and correlate these with flow properties such as angle of repose, jamming probability, segregation effects, and rheological shear strength.A final objective related to the broader impacts of this proposal is the scientific training of undergraduate research students in a highly interdisciplinary research environment. This project will directly involve the training of up to six undergraduate researchers over the duration of the program, but it is expected that up to ten will likely be impacted including unpaid research for credit during the academic year. In addition, we plan to hire a high school teacher for the summer of year 2, in order to continue one of JMU's missions of educating teachers. The students will be exposed to issues in materials science and complex systems, including rheology, dynamics, and image processing. The participants in this program will be expected to participate in activities related to the NSF Research Experiences for Undergraduates (REU) sites in chemistry and materials science at JMU to become part of a "community of scholars" with over sixty other summer undergraduate researchers in chemistry and materials science at JMU. In summary, this program helps serve to broadly impact the pipeline of future scientists from the high school through the graduate level with students trained in cutting-edge research in multiphase flows.