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，既表现出流体的力学性质，也表现出固体的力学性质。当粘弹性流体穿过多孔材料时，表现出突然向混沌流动的转变，这是强化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。尽管我们对简单模型几何中的粘弹性流动有深入的了解，但预测它们在复杂的、不规则的多孔材料缝隙中的流动特性仍然是一个突出的挑战。这项工作的目的是量化粘弹性流体在一系列模型和现实的多孔介质中的流动，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性质。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，最大限度地减少聚合物加工中的电力消耗和成本，并了解影响土壤生态和人类感染的生物膜机理。在该项目下，将组织研讨会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，这项工作的各个方面将被整合到微流体学和复杂流体课程中。粘弹性流体在多孔介质中流动的稳定性强烈依赖于连续孔隙的无序和连通性。弹性应力的记忆将平流与孔隙微结构耦合在一起，形成了极其复杂的稳定性标准，并强调了需要考虑聚合物流动的拉格朗日特性。缺乏对相关二维和三维流动几何结构的定量研究，往往会产生相互矛盾的结果，并抑制了我们预测这些系统弥散输运性质的能力。为了解决我们目前对粘弹性渗流的认识中的这些主要缺陷，我们将通过微流体实验和数值模拟相结合的方法来实现以下主要目标：(1)确定几何结构、无序和孔隙率对二维多孔介质流动中粘弹性不稳定性的作用。(2)通过对拉格朗日相干结构的分析，建立了几何和粘弹性对多孔介质中弥散的影响。(3)阐明了三维在多孔介质流动的粘弹性稳定性及其输运特性中的作用。这项工作将在流体应力、拉伸运动学和运输之间建立直接联系。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。

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.