Development of a thermodynamically consistent, robust model for thixotropic suspensions

1235863瓦格纳一个具有挑战性的科学和工程问题是准确预测含有固体颗粒的复杂流体的流动，如纳米颗粒、胶体、晶体和大颗粒。这种悬浮液存在于各种各样的消费品（如油漆、化妆品和食品）、自然界（如沉积物、浓缩蛋白溶液和血液）以及国家关注的多相流体（如超铀罐污泥）中，并作为新兴储能设备（液流电池）的关键部件。这种悬浮液的流动通常是触变性的，因此材料的流变特性取决于时间和流动历史。拟议的研究通过一种变革性的方法来解决这一挑战，即开发一种基于多尺度微结构的框架，该框架将在热力学上保持一致，并普遍适用于所有流动。一个关键的组成部分将是确定正确定义微观结构的内部变量。理论和模型的验证将通过利用新实验技术的互补发展来同时测量这些系统的流变学和微观结构来完成。因此，对定义良好的模型触变系统进行系统的、理论与实验相结合的研究是研究计划的重要组成部分。该研究的智力优点包括开发了一个强大的，理论上严谨的框架，用于模拟一般的，随时间变化的浓缩悬浮液流。这种系统的和综合的努力将导致复杂触变系统的建模和理解的新能力，可以显著地帮助工业和国家重要性的许多材料的合理工程。这项工作的广泛影响包括培养工业和学术研究所需的悬浮流变学博士和理学学士。通过建立和改进目前的实验室演示，将开发用于K-12教育的模块。本研究中开发的模型和知识有潜力改善许多行业，因为触变悬浮液的加工和流动对化学品，材料和制药制造和处理至关重要。作为一项特别重要的应用，PIs将与桑迪亚国家实验室的伙伴合作，解决处理汉福德放射性储罐污泥悬浊液的国家挑战以及有关核废料管理的其他关键问题。

1235863WagnerA challenging scientific and engineering problem is accurately predicting the flow of complex fluids containing solid particles, such as nanoparticles, colloids, crystals and larger particulates. Such suspensions are encountered in a wide array of consumer products (e.g. paints, cosmetics, and foods), in nature (e.g. sediments, concentrated protein solutions and blood), as well as multiphase fluids of significant national concern (e.g. transuranic tank sludge), and as critical components in emerging devices for energy storage (flow batteries). The flow of such suspensions are often thixotropic, whereby the material's rheological properties are time and flow history dependent. The proposed research addresses this challenge though a transformative approach, namely developing a multiscale microstructure-based framework that will be thermodynamically consistent and generally applicable for all flows. A key component will be to identify the internal variables that properly define the microstructure. Validation of the theory and modeling will be accomplished by leveraging a complementary development of new experimental techniques to simultaneous measure the rheology and microstructure of such systems. Thus, a systematic, combined theoretical/experimental investigation on well-defined, model thixotropic systems is an important component of the research plan. The intellectual merits of the research include the development of a robust, theoretically rigorous framework for modeling the general, time dependent flow of concentrated suspensions. This systematic and integrated effort will lead to a new capability in the modeling and understanding of complex thixotropic systems that can significantly aid in the rational engineering of many materials of industrial and national importance. The broader impacts of this work include educating PhDs and BCHEs in suspension rheology necessary for careers in industry and academic research. Modules are to be developed for K-12 education by building on and improving current laboratory demonstrations. The models and knowledge developed in this research have potential to improve many industries as the processing and flow of thixotropic suspensions is critical to chemicals, materials, and pharmaceutical manufacturing and handling. As an application of particular importance, the PIs will be working with partners at Sandia National Laboratory to address the national challenge of processing suspensions of radioactive tank sludge at Hanford and other critical issues concerning nuclear waste management.