Stability of Partially Wetting Droplet in Wind

主要研究者：Lee，Sungyon提案编号：1605947拟议研究的目标是调查在侧风作用下部分润湿表面的液滴的行为。表面是不完美的，更像是真实的表面。每天的应用包括窗户上的水滴运动、飞机的除冰、化学处理设备（例如，冷凝器中）、喷墨打印和环境（其中雨滴或喷雾滴在树叶表面上移动）。粘附在表面上然后在风或重力下流动的水滴在自然界中无处不在。 液滴脱钉阈值的预测是流体力学中的一个基本问题，并且与许多其他工程问题相关。虽然理论存在于低雷诺数区域，但由于与边界层分离相关的非定常性，在工程感兴趣的高雷诺数区域，问题变得更加复杂。本提案的总体目标是通过简化建模和最先进的实验测量技术，从根本上了解部分润湿液滴在高雷诺数状态下的稳定性极限。建议的工作重点是开发一个理论模型，捕获液滴动力学的存在下，分离的边界层流动。新开发的液滴模型结合了外部风的影响，在时间平均的意义上，以规避所产生的困难，从固有的不稳定性的流动和液滴表面振荡。初步结果表明，该模型有效地匹配的稳定性限制的一个单一的液滴在粗糙表面的宏观性质，并扩展到包括固体突起的影响。与此同时，将进行测量仪器的额外开发，以可视化液滴周围的不稳定气流，并提高理论验证所需的接触角测量性能。该项目更广泛的影响包括德克萨斯州高中科学项目的推广活动。液滴的问题是一个有吸引力的科学推广，因为液滴脱钉是同时熟悉但难以理解。这个项目将以液滴为例，说明高中数学和物理中引入的抽象概念如何解释物理世界中的现象。PI将邀请高中科学教师在实验室工作，并根据实验开发课程。这些教师将向他们的班级提供这些内容，并在德克萨斯州每年举办的教师峰会上报告他们的经验。

PI: Lee, SungyonProposal Number: 1605947The goal of the proposed research is to investigate the behavior of drops that partially wet surfaces under the effect of a cross-wind. The surfaces are imperfect, more like realistic surfaces. Every day applications include the motion of drops on windows, the de-icing of airplanes, chemical process equipment (e.g., in condensers), ink jet printing, and the environment (where rain drops or spray drops move on leave surfaces).Water droplets that adhere to surfaces then run under wind or gravity are ubiquitous in nature. Prediction of droplet depinning thresholds is a problem of fundamental importance in fluid mechanics and is relevant to many other engineering problems. While theories exist in the low Reynolds number regime, the problem becomes more complex in the high-Reynolds-number regime of engineering interest due to the unsteadiness associated with boundary layer separation. The overall objective of this proposal is to gain fundamental understanding of the stability limits of a partially-wetting droplet in the high Reynolds number regime, through reduced modeling and state-of-art experimental measurement techniques. The proposed work focuses on the development of a theoretical model that captures the droplet dynamics in the presence of the separated boundary layer flow. The newly developed droplet model incorporates the effects of the external wind in a time-averaged sense to circumvent the difficulties arising from inherent unsteadiness of the flow and droplet surface oscillations. Preliminary results show that the model effectively matches the stability limits of a single droplet on a rough surface in terms of macroscopic properties and is extended to include the effect of solid protuberance. In parallel, additional development of the measurement instrument will be conducted to visualize the unsteady air flow around the droplet and to improve the performance for contact-angle measurements necessary for theoretical validation. The broader impacts of the project include outreach activities for high school science programs in Texas. The droplet problem is an attractive one for science outreach because droplet depinning is simultaneously familiar yet difficult to understand. This project will use droplets as an example that illustrates how abstractions introduced in high school math and physics can explain phenomena seen in the physical world. The PIs will invite high-school science teachers to work in the lab and to develop curriculum based on the experiment. These teachers will deliver this content to their classes and report on their experiences at a teachers' summit hosted annually at Texas A&M.