Collaborative Research: Stability and dispersion of viscoelastic flows through porous media

粘弹性流体，包括聚合物和生物材料，具有流体和固体两种力学特性。当被驱动通过多孔材料时，粘弹性流体表现出突然过渡到混沌流动，这是增强混合的一个关键特征，它调节了大量重要的地质、生物和工业过程。尽管我们对简单几何模型中的粘弹性流动有深入的了解，但预测它们在多孔材料复杂、不规则裂缝中的流动特性仍然是一个突出的挑战。这项工作的目标是量化粘弹性流体在一系列模型和现实多孔介质中的流动，并确定微观几何形状如何影响粘弹性流体的宏观流动和输运特性。该项目的成果将直接影响岩石和土壤中的提取和生物修复效率，最大限度地降低聚合物加工的功耗和成本，以及了解影响土壤生态和人类感染的生物膜力学。在该项目下，将组织讲习班以促进该领域科学家的早期职业发展，几名本科生和研究生将接受研究培训，并将这项工作的各个方面纳入微流体和复杂流体课程。粘弹性流体在多孔介质中流动的稳定性很大程度上取决于连续孔隙的无序性和连通性。弹性应力的记忆耦合了平流和孔隙微观结构，使得稳定性判据非常复杂，并强调需要考虑聚合物流动的拉格朗日特性。由于缺乏对相关二维和三维流动几何的定量研究，得出的结果往往相互矛盾，并且抑制了我们预测这些系统色散输运性质的能力。为了解决我们目前对多孔介质粘弹性流动理解中的这些关键缺陷，将通过微流体实验和数值模拟的结合来实现以下主要目标：(1)确定二维多孔介质流动中几何结构、无序度和孔隙度对粘弹性不稳定性的作用。(2)通过分析拉格朗日相干结构，建立几何和粘弹性对多孔介质中弥散的影响。(3)阐明三维在多孔介质流动粘弹性稳定性和由此产生的输运特性中的作用。这项工作将建立流体应力、拉伸运动学和运输之间的直接联系。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Viscoelastic fluids, including polymers and biological materials, exhibit mechanical properties of both fluids and solids. When driven through porous materials, viscoelastic fluids exhibit an abrupt transition to chaotic flow, which is a key feature of enhanced mixing that regulates a vast array of important geological, biological, and industrial processes. Despite our deep understanding of viscoelastic flows in simple model geometries, predicting their flow properties through the intricate, irregular crevices of porous materials remains an outstanding challenge. The goal of this work is to quantify viscoelastic fluid flows in a range of model and realistic porous media and determine how microscopic geometry affects the macroscopic flow and transport properties of viscoelastic fluids. The outcomes of this project will have direct implications for extraction and bioremediation efficiency in rock and soil, minimizing power consumption and cost in polymer processing, and understanding biofilm mechanics that affect soil ecology and infections in humans. Under this project, workshops will be organized to promote early career development of scientists in the field, several undergraduate and graduate students will receive research training, and aspects of this work will be integrated into microfluidics and complex fluids courses.The stability of viscoelastic fluid flows through porous media strongly depends upon the disorder and connectivity of successive pores. The memory of elastic stresses couples advection to pore microstructure making for exquisitely complex stability criteria, and emphasizing the need to consider the Lagrangian character of polymeric flows. A dearth of quantitative studies across relevant two- and three-dimensional flow geometries has yielded often conflicting outcomes and has inhibited our ability to forecast the dispersive transport properties of these systems. To resolve these key deficiencies in our current understanding of viscoelastic flows through porous media, the following principle aims will be achieved through the integration of microfluidic experiments and numerical simulations: (1) Determine the role of geometrical structure, disorder, and porosity on viscoelastic instability in two-dimensional porous media flows. (2) Establish the effect of geometry and viscoelasticity on dispersion in porous media through analysis of Lagrangian coherent structures. (3) Elucidate the role of three-dimensionality in the viscoelastic stability and resultant transport properties of porous media flows. This work will establish a direct link between fluid stress, stretching kinematics, and transport.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.