The Dynamics of Curved Fluid Films Between Complex Interfaces

薄膜的动力学对于液滴的结合、泡沫的稳定性、各种润滑剂的作用以及各种“干燥”现象，包括油漆和涂层的流平性，都是至关重要的。在我们的体内，薄薄的液体膜在一系列广泛的过程中发挥着关键作用，包括吸入后净化空气的能力，通过所谓的“泪膜”在各种条件下看清东西的能力，以及单个红细胞在毛细血管中转移氧气的能力。现在已经知道，并且在过去十年的实验中反复证明，薄膜中非常小的不均匀(即杂质)产生的薄膜厚度图案可能是时间依赖的和混乱的。这些动力甚至会导致一种新的“湍流”。人们对这些复杂图案的形成缺乏物理上的了解，一旦它们出现，就完全控制了薄膜的寿命和演变。因此，例如，它们可以确定泡沫是稳定的还是不稳定的，或者润滑剂是失效还是仍然有用。这项研究结合了理论、数值模拟和实验，以发展对这些复杂的动力学和它们可能发生的条件的物理理解。在研究中学到的知识将在斯坦福大学的两个班级中传播，三名高中教师将通过暑期实习参与研究，斯坦福大学明星-通过艺术进行科学教学-计划将突出这些电影动态的自然美，并在视觉上开发吸引人的故事，以满足包括高中和社区大学生在内的广大观众。为了实现对这些薄膜混沌动力学的理解，研究将通过润滑剂或“薄膜”理论使用直接数值模拟(DNS)-因此，即使在“薄膜”假设下，也需要大量的数值解决方案。这项研究将通过数值模拟来阐明与以前完成的实验相关的参数模式，这些模式的形成条件和机制是什么。这些模拟将与额外的实验相结合，以直接测试是否成功地模拟了新的物理理解。该研究的目标是勾勒出先前关于空间和时间发展的简化假设不成立的参数体系，从而从根本上改变复杂界面之间的薄膜动力学研究。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。

The dynamics of thin films are critical to the coalescence of drops, foam stability, the action of lubricants of all types, as well as, “drying’’ phenomena of all kinds, including the levelling of paints and coatings. In our bodies, thin fluid films play a key role in a wide array of processes including the cleaning of the air after inhalation, the ability to see clearly under all kinds of conditions through the so-called “tear film”, and the ability of single red blood cells to transfer oxygen in capillaries. It is now known and has been demonstrated repeatedly in experiments over the last decade that very small inhomogeneities in the films (i.e. impurities), generate film thickness patterns that can be time dependent and chaotic. These dynamics can even lead to a new kind of “turbulence”. There is very little physical understanding of the formation of these complex patterns, which, once they appear, completely control the lifetime and evolution of the thin films. So, for example, they determine whether a foam is stable or unstable or whether a lubricant fails or remains useful. The research integrates theory, numerical simulations, and experiments to develop a physical understanding of these complex dynamics and the conditions in which they may occur. The knowledge learned during the research will be disseminated in two classes at Stanford, three high school teachers will be involved in the research with summer internships, and the Stanford STAR – Scientific Teaching Through Art – program will highlight the natural beauty of the dynamics of these films and visually develop appealing stories to reach a broad audience including high school and community college students.To accomplish the understanding of these thin film chaotic dynamics the research will employ direct numerical simulation (DNS) via a lubrication or “thin film” theory– thus even with the “thin film” assumption a large numerical solution is required. The research will elucidate via numerical simulation over parameter regimes associated with previously accomplished experiments, what are the conditions and mechanisms for the formation of these patterns. The simulations will be coupled with additional experiments to directly test whether a new physical understanding has been successfully modelled. The research goal is to delineate the parameter regimes where prior simplifying assumptions regarding space and time development are not valid, thus fundamentally changing the study of thin film dynamics between complex interfaces.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.