Exploring Flow Enhancements of Hydrophobic Particles in Confined Fluid Flow

疏水性颗粒，这是特殊的涂层，使表面光滑，在环境工程和能源科学的许多应用中发挥着至关重要的作用。例如，由于其长期运输稳定性，疏水颗粒已被用于减轻地下水/废水污染并改善强化采油。因此，更好地了解这些颗粒的运输和归宿是实现人类健康，福祉和社会效益的可持续资源的重要一步。尽管有这些关键的社会和技术影响，但由于其复杂的动力学，疏水颗粒的物理学尚未在理论上得到充分解释，也没有在模拟和实验中重现。该项目旨在深入了解提高疏水颗粒可运输性的关键运输机制。该项目还将促进广泛的外联活动，如移动的实验室，专门针对农村地区，弥合城乡教育差距。该项目的目标是通过计算机建模和模拟沿着微流体实验验证来阐明封闭悬浮液中疏水颗粒的动力学和流变学。基于斯托克斯动力学方法的高保真模拟将被应用于研究各种疏水性，如涂层性能，对悬浮液中颗粒动力学的影响。中心假设是，颗粒表面上的疏水性的存在将增强其可运输性，这是由于增强的颗粒向几何形状的中心的迁移，特别是在高浓度下的限制。为实现这一目标，本论文的具体目标是：1）建立一个疏水颗粒的数学模型，该模型中的滑移速度可以根据局部浓度和流动强度而变化; 2）建立一个计算框架来有效地模拟受限条件下疏水颗粒的悬浮液; 3）阐明剪切悬浮液的动力学和流变学;以及4）使用微流体实验验证计算结果以改进模型和基本假设。在高浓度下可以增强颗粒迁移的发现自然表明存在非平凡的流变行为。在这方面，与检查浓缩悬浮液有关的一个广泛主题是剪切增稠。因此，该项目有望提供一个新的理解剪切增稠，可以通过表面疏水性调整。这一新知识在广泛的应用领域具有深远的影响，因为剪切增稠被广泛应用于国防和环境系统。该奖项反映了NSF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。

Hydrophobic particles, which are specially coated to make the surface slippery, play a crucial role in many applications in environmental engineering and energy science. For example, hydrophobic particles have been used to mitigate groundwater/wastewater contamination and improve enhanced oil recovery due to their long-term transport stability. Therefore, a better understanding of the transport and fate of such particles is an essential step towards sustainable resources for human health, well-being, and societal benefits. Despite these critical social and technological impacts, the physics of hydrophobic particles have not yet been fully explained theoretically nor reproduced in simulations and experiments due to their complex dynamics. This project is to provide a deep understanding of the key transport mechanisms enhancing the transportability of hydrophobic particles. The project will also promote extensive outreach activities, such as mobile labs, to specifically target rural areas and bridge the urban-rural divide in education.The goal of this project is to elucidate the dynamics and rheology of hydrophobic particles in a confined suspension via computational modeling and simulations along with microfluidic experimental validation. High-fidelity simulations based on the Stokesian dynamics approach will be applied to study the effects of various hydrophobicity, such as coating properties, on particle dynamics in a suspension. The central hypothesis is that the presence of hydrophobicity on the particle surface will enhance its transportability due to an enhanced particle migration toward the center of the geometry, especially at high concentrations under confinement. In pursuit of this goal, the specific objectives are: 1) establish a mathematical model for hydrophobic particles in which slip velocity can vary depending on local concentrations and flow strengths; 2) establish a computational framework to efficiently simulate a suspension of hydrophobic particles under confinement; 3) elucidate the dynamics and rheology of the sheared suspension; and 4) validate the computational results using microfluidic experiments to improve the model and underlying assumptions. The discovery that particle migration can be enhanced at high concentrations naturally suggests the existence of non-trivial rheological behaviors. In this regard, one broad theme related to examining concentrated suspensions is shear-thickening. Thus, this project is expected to provide a new understanding of shear-thickening that could be tuned by surface hydrophobicity. This new knowledge has far-reaching implications in a broad spectrum of applications because shear-thickening is widely adopted in defense and environmental systems.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.