ERI: Evolution of Detached Liquid Sheet Edges from Patterned Boundaries

液体薄片在其边缘破碎形成液滴的复杂方式对于了解喷雾特性非常重要，例如产生的液滴的最终尺寸。由于喷雾在许多涉及液体的自然和工程场景中都会遇到，因此对它们的研究在基础和应用层面都很重要。本项目的目的是开发一个实验平台，以探索微图案化边界在液体薄片边缘演变和随后破裂中的作用。项目结果可用于验证破碎机理的数值和计算研究。该项目是工程研究启动计划的一部分，将在一所主要为本科生服务的高等教育机构进行，并将为现有以项目为基础的课程的学生群体提供开发实验设备的机会。更多的学生将从现有的校园项目中受益，其中一个项目直接与大学改善和促进STEM的多样性、公平性和包容性的努力捆绑在一起，提供极好的指导和职业发展机会。该项目的目标是通过调查微尺度图案对一旦液膜分离后产生边缘的物理边界的影响，来改进探索液膜边缘破裂的实验，液膜边缘是通过喷雾形成液滴的基础。以前的实验使用金属线框的快速加热来形成液体膜(肥皂膜)的边缘。这个项目计划回答的关键问题是：(1)代替使用未掺杂的金属丝形成液膜的初始边缘，用于分离实验，使用快速沸腾来释放边缘，是否可以用微尺度图案创建边缘或边界，以在液膜边缘上诱导已知空间波长的扰动？(2)如果可能，调制扰动对边缘演化的影响的性质是什么？(3)那么是否有可能证明调制不稳定性增长的测量结果，以明确地确定最快增长波长，以通过不稳定性进一步了解演化和破裂，分离的液体薄片边缘？为了回答这些问题，将进行具有挑战性的实验，使用高速摄影和高空间分辨率。通过开发这些实验技术来回答关键问题，该项目将为未来液体薄片破裂的研究提供有用的途径。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 complex ways in which sheets of liquid break up at their edges to form droplets are important to the understanding of spray characteristics, for example the eventual size of the droplets produced. As sprays are encountered in numerous natural and engineered scenarios involving liquids, their study is important both at a fundamental and applied level. The aim of this project is to develop an experimental platform to explore the role of micropatterned boundaries on the evolution and subsequent breakup of liquid sheet edges. Project results can be used to validate numerical and computational studies of breakup mechanisms. The project, part of the Engineering Research Initiation program, will take place at a primarily undergraduate serving institution of higher education and will give student groups from existing project-based courses the opportunity to develop experimental equipment. Additional student participants will benefit from existing campus programs - one of which is directly tied to university efforts at improving and promoting diversity, equity, and inclusivity in STEM – providing excellent mentoring and professional development opportunities. The goal of this project is to improve experiments to explore the breakup of liquid sheet edges, fundamental to the formation of droplets by sprays, by investigating the influence of micro-scale patterns on the physical boundaries from which the edges are created once liquid sheets are detached. Previous experiments have used rapid heating of metal wire frames to form the edges of liquid films (soap films). The key questions this project proposes to answer are: (1) Instead of using an unadulterated metallic wire to form the initial edge of a liquid sheet for detachment experiments that use rapid boiling to free the edge, can an edge, or boundary, be created with micro-scale patterns to induce disturbances of a known spatial wavelength onto that liquid film edge? (2) If this is possible, what is the nature of the influence of the modulated disturbance on the evolution of the edge? (3) Is it then possible to demonstrate measurements of modulated instability growth to determine, without ambiguity, fastest growing wavelengths to further understand the evolution and breakup, via instability, of the detached liquid sheet edge? To answer these questions, challenging experiments using high-speed photography and at high spatial resolution will be performed. By developing these experimental techniques to answer the key questions, the project will provide useful avenues for future study of liquid sheet breakup.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.