A New Stress Bearing Mechanism in Non-Newtonian Fluids

非牛顿流体中的一种新的应力承载机制

• 批准号: 0932600
• 负责人: Robert Deegan
• 金额: $ 30万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0932600&HistoricalAwards=false
• 关键词: New; Stress; Bearing; Mechanism; Non

Deegan 0932600The PI discovered two phenomena, persistent holes and negative flows, which together suggest that shear-thickening complex fluids possess a vibration-activated stress-bearing mechanism. A persistent hole can maintain a stable free surface oriented parallel to gravity. Negative flows are flows that are opposite to the mean applied stress. Laboratory experiments and modeling will reveal the origin of these phenomena which the PI believes have the same physical origin. The PI will study the two classes and develop a rheological model based on these results in collaboration with Ronald Larson and develop and validate a free surface model based the flow measurements and the rheological model in collaboration with Rich Kerswell. The experiments will be conducted on a vibrating test platform and in a custom built shear cell using Particle Image Velocimetry. The rheology will be characterized with a commercial stress-controlled rheometer. The fluid structure will be characterized using particle tracking, light scattering microscopy, and confocal microscopy. The flow field measurements combined with the rheological model will help build and validate a hydrodynamic model of persistent holes and negative flows. The structural characterization will reveal the link between the microscopic structure and the rheological behavior. The results of this study will be of interest broadly to complex fluids community and specifically to the shear banding, shear thickening, and jamming communities. It will also be of interest to the many industries - from plastics to cosmetics to pharmaceuticals - in which non-Newtonian fluids are commonly used. This study has the potential to reveal a fundamental mechanism in complex fluids which may be as significant as normal stress or extensional viscosity. The PI's educational program builds on his YouTube video of persistent holes, that has been viewed over 2.5 million times and on an exhibit in the final stages of development at the San Francisco Exploratorium. In addition, the PI will develop and teach a new laboratory course on nonlinear science in the interdisciplinary Center for the Study of Complex Systems. Undergraduates participating in summer internships in the PI's lab will benefit from an increased awareness of career opportunities in science and competitiveness for graduate school entry.

Deegan 0932600 PI发现了两种现象，持续的孔和负流，它们共同表明剪切增稠复杂流体具有振动激活的应力承载机制。一个持久的洞可以保持一个稳定的自由表面定向平行于重力。负流动是与平均施加应力相反的流动。实验室实验和建模将揭示这些现象的起源，PI认为这些现象具有相同的物理起源。PI将研究这两个类别，并与罗纳德Larson合作开发基于这些结果的流变模型，并与Rich Kerswell合作开发和验证基于流量测量和流变模型的自由表面模型。实验将在振动测试平台上进行，并使用粒子图像测速仪在定制的剪切单元中进行。流变学将用商业应力控制流变仪表征。将使用粒子跟踪、光散射显微镜和共聚焦显微镜来表征流体结构。流场测量与流变模型相结合，将有助于建立和验证持续孔和负流的水动力学模型。结构表征将揭示微观结构和流变行为之间的联系。这项研究的结果将广泛感兴趣的复杂流体社区，特别是剪切带，剪切稠化，堵塞社区。它也将是许多行业的兴趣-从塑料到化妆品到制药-其中非牛顿流体是常用的。这项研究有可能揭示一个基本的机制，在复杂的流体，这可能是显着的正常应力或拉伸粘度。PI的教育计划建立在他的YouTube视频的持续孔，已被观看超过250万次，并在展览的最后阶段的发展在旧金山弗朗西斯科探索。此外，PI将在跨学科的复杂系统研究中心开发和教授非线性科学的新实验室课程。参加PI实验室暑期实习的本科生将受益于对科学职业机会的认识提高和研究生入学竞争力。