Rheology and fluid dynamics of surfactant solutions with flow-induced structure

具有流动诱导结构的表面活性剂溶液的流变学和流体动力学

• 批准号: 1803090
• 负责人: Michael Graham
• 金额: $ 30万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-15 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1803090&HistoricalAwards=false
• 关键词: Rheology; fluid; dynamics; surfactant; solutions

Surfactants are molecules comprised of a head that is water soluble bonded to an oily tail that repels water. Because of this dual nature, surfactants dissolved in water form assemblages called micelles, in which the oily tails form the center, separated from the surrounding water molecules by the water-preferring head groups. Micellar surfactant solutions are used in a wide range of applications from fracking fluids in the oil and gas industry to heat-transfer fluids in the chemical process industries to various personal care and cleaning products. During flow, surfactant solutions that form long thin "wormlike" micelles undergo a process where individual micelles combine to form much larger assemblages. These are called flow-induced structures and can have dramatic effects on the flow properties of the solution. These structures form in turbulent flow of wormlike micelle solutions leading to substantial reduction in the energy cost for pumping the fluid. Despite the increasingly frequent application of these so-called drag-reducing surfactant systems, this structure-formation phenomenon remains poorly understood. This work will advance the development of mathematical models for predicting the flow behavior of wormlike micelle solutions and use these models to understand why they are so effective in reducing energy consumption in flow processes. The project will also involve a substantial outreach component: in a service-learning course, undergraduate engineering students will develop project-based lessons in fluid mechanics and then go out to the Boys and Girls Clubs to share these with kids from underserved minority populations.The long-term aim underlying this project is (1) development of models for self-assembling complex fluids like micellar solutions that areas computationally tractable for fluid dynamics analyses, and (2) use of these models to generate insights and predictions into the behavior of this class of fluids in flows characteristic of engineering applications. The work will further develop a recently-proposed micromechanical constitutive model called the reactive rod model, putting it firmer physical ground and making extensive comparisons to experimental data. It will also analyze the flow of an structure-forming fluid in a circular Couette device, where many of the interesting features of flow-induced structure in surfactant solutions have been studied experimentally. Finally, it will elucidate the interaction between turbulence, flow-induced structure and drag reduction using computations with the model. Comparisons with results for polymer solutions will be made, to uncover differences between turbulent drag reduction in polymer and surfactant solutions. Furthermore, comparisons of simulation results with experimentally observed features of turbulence in surfactant solutions will be made. Flow-induced structure formation is widespread in complex fluids and this work takes first steps into analysis of the fluid dynamics of these materials and thus toward new insights into the origins and consequences of their fascinating behavior.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

表面活性剂是由可溶于水的头部与排斥水的油性尾部结合而成的分子。由于这种双重性质，表面活性剂溶解在水中形成称为胶束的组合体，在胶束中，油性尾巴形成中心，通过亲水的头部基团与周围的水分子分开。胶束表面活性剂解决方案应用广泛，从石油和天然气行业的水力压裂液到化工过程行业的传热液，再到各种个人护理和清洁产品。在流动过程中，形成细长的“蠕虫状”胶束的表面活性剂溶液经历了一个过程，单个胶束结合形成更大的集合。这些结构被称为流动诱导结构，可以对溶液的流动性质产生重大影响。这些结构在蠕虫状胶束溶液的湍流中形成，从而大大降低了泵送流体的能源成本。尽管这些所谓的减阻表面活性剂体系的应用越来越频繁，但这种结构形成现象仍然鲜为人知。这项工作将推动预测蠕虫状胶束溶液流动行为的数学模型的发展，并利用这些模型来理解为什么它们在流动过程中如此有效地降低能量消耗。该项目还将包括一个重要的推广部分：在服务性学习课程中，工科本科生将开发基于项目的流体力学课程，然后到男孩和女孩俱乐部与服务不足的少数族裔的孩子们分享这些课程。该项目的长期目标是(1)开发自组装复杂流体的模型，如胶束溶液，其区域易于计算，用于流体动力学分析，(2)使用这些模型来洞察和预测这类流体在具有工程应用特征的流动中的行为。这项工作将进一步发展最近提出的被称为反应杆模型的微观机械本构模型，使其具有更坚实的物理基础，并与实验数据进行广泛的比较。它还将分析结构形成流体在圆形Couette装置中的流动，在该装置中，已经通过实验研究了表面活性剂溶液中流动诱导结构的许多有趣特征。最后，通过模型的计算，阐明了湍流、流致结构和减阻之间的相互作用。将与聚合物溶液的结果进行比较，以揭示聚合物溶液和表面活性剂溶液中湍流减阻之间的差异。此外，还将把模拟结果与实验观察到的表面活性剂溶液中的湍流特征进行比较。流动诱导结构的形成在复杂的流体中广泛存在，这项工作是分析这些材料的流体动力学的第一步，从而对其迷人行为的起源和后果有了新的见解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Constitutive modeling of dilute wormlike micelle solutions: Shear-induced structure and transient dynamics

• DOI: 10.1016/j.jnnfm.2021.104606
• 发表时间: 2021-07-13
• 期刊: JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
• 影响因子: 3.1
• 作者: Hommel, Richard J.;Graham, Michael D.
• 通讯作者: Graham, Michael D.