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，表现出流体和固体的机械性能。当被驱动通过多孔材料时，粘弹性流体表现出向混沌流动的突然转变，这是增强混合的关键特征，其调节大量重要的地质、生物和工业过程。尽管我们对简单模型几何形状中的粘弹性流动有着深刻的理解，但通过多孔材料的复杂、不规则裂缝预测其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流动的范围内的模型和现实的多孔介质，并确定微观几何形状如何影响宏观流动和粘弹性流体的传输特性。该项目的成果将直接影响岩石和土壤的提取和生物修复效率，最大限度地减少聚合物加工的功耗和成本，并了解影响土壤生态和人类感染的生物膜力学。在该项目下，将组织研讨会以促进该领域科学家的早期职业发展，一些本科生和研究生将接受研究培训，这项工作的各个方面将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强烈依赖于连续孔隙的无序性和连通性。记忆的弹性应力耦合对流孔隙微结构，使精致复杂的稳定性标准，并强调需要考虑的拉格朗日性质的聚合物流。缺乏相关的二维和三维流动几何形状的定量研究，往往产生相互矛盾的结果，并抑制了我们预测这些系统的分散输运特性的能力。为了解决目前多孔介质粘弹性流动研究中存在的主要不足，本文将通过微流控实验和数值模拟相结合的方法，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影响。(2)通过分析拉格朗日拟序结构，建立几何形状和粘弹性对多孔介质中色散的影响。(3)阐明三维性在粘弹性稳定性和多孔介质流动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NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.