A study of the dynamics of drop impact: Impact forces, pressure and shear stress distributions

跌落冲击动力学研究：冲击力、压力和剪应力分布

• 批准号: 2017071
• 负责人: Xiang Cheng
• 金额: $ 30.15万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2017071&HistoricalAwards=false
• 关键词: study; dynamics; drop; impact; Impact

From raindrops battering on a windshield to coffee splashing on a table, drop impact is ubiquitous in our daily life and relevant to many important natural and industrial processes. Although the phenomenon has been studied for many decades, the understanding of drop impact is still far from complete due to the complexity associated with typical fast impact processes. Significant progress has been made on drop impact in recent years using high-speed photographic techniques. Relying on direct imaging, most experiments focused on the kinematics of drop impact, i.e., the shape of impacting drops. Few studies have probed the dynamic properties of drop impact such as its impact force, pressure and shear stress. These dynamic quantities lead to the most important outcome of an impact event and affect a wide range of phenomena, including soil erosion, impact-induced wear/damage and the survival of living organisms exposed to the elements. The goal of this research is to conduct a systematic study on mapping the dynamic aspects of drop impact under different conditions. The research will develop a new experimental technique, 3D high-speed stress microscopy, to measure the impact force, pressure, and shear stress of drop impact with high spatial and temporal resolutions. The project will provide a fundamental understanding of the dynamics of drop impact in unexplored regimes and a practical guideline to control impact forces and mitigate impact-induced damage on solid substrates. The project will also provide a unique opportunity to introduce frontier research in undergraduate curriculum and forge collaborations with coating companies. By combining traction force microscopy with high-speed photography, the research will construct a 3D high-speed stress microscope to measure the temporal variation of pressure and shear stress distributions beneath an impacting drop during a fast impact process. With the new technique, the project will verify previous theoretical predictions, including the singular dynamics of off-center pressures, the scaling relation of drag forces, and the propagation of boundary layers in spreading drops. As such, the study will reveal the dynamics of drop impact in spatiotemporal regimes, inaccessible to conventional kinematic measurements. Moreover, the research will examine the influence of different surface properties such as stiffness, wettability, and micro-textures on the stress distributions. The study aims to seek optimal surface designs, which can substantially reduce impact-induced wear and damage.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.

从挡风玻璃上的雨滴到桌子上的咖啡溅到桌子上，在我们的日常生活中，掉落的影响无处不在，并且与许多重要的自然和工业过程有关。尽管已经研究了数十年的现象，但由于与典型的快速影响过程相关的复杂性，对跌落影响的理解仍然远远不够完整。近年来，使用高速摄影技术在跌落影响方面取得了重大进展。依靠直接成像，大多数实验都集中在滴撞击的运动学上，即撞击滴的形状。很少有研究探讨了跌落撞击的动态特性，例如其撞击力，压力和剪切应力。这些动态量导致撞击事件的最重要结果，并影响广泛的现象，包括土壤侵蚀，撞击引起的磨损/损伤以及暴露于元素的生物的生存。这项研究的目的是进行系统研究，以绘制在不同条件下降落影响的动态方面。这项研究将开发一种新的实验技术，即3D高速应力显微镜，以测量使用高空间和时间分辨率的跌落撞击的影响力，压力和剪切应力。该项目将提供对未开发政权下降影响动态的基本理解，以及控制影响力并减轻撞击引起的对固体底物的损害的实用指南。该项目还将提供一个独特的机会，以引入本科课程中的边境研究，并与涂料公司锻造合作。通过将牵引力显微镜与高速摄影相结合，该研究将构建3D高速应力显微镜，以测量在快速冲击过程中撞击下降下方压力和剪切应力分布的时间变化。通过新技术，该项目将验证以前的理论预测，包括偏心压力的奇异动态，阻力力的缩放关系以及在扩散下降中边界层的传播。因此，该研究将揭示时空状态下降低影响的动力学，而传统运动学测量无法访问。此外，该研究将研究不同表面特性的影响，例如刚度，润湿性和微文字对压力分布。该研究旨在寻求最佳的表面设计，从而大大减少影响引起的磨损和损害。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准通过评估来支持的。

项目成果

Drop Impact Dynamics: Impact Force and Stress Distributions

• DOI: 10.1146/annurev-fluid-030321-103941
• 发表时间: 2022-03-01
• 期刊: ANNUAL REVIEW OF FLUID MECHANICS
• 影响因子: 27.7
• 作者: Cheng, Xiang;Sun, Ting-Pi;Gordillo, Leonardo
• 通讯作者: Gordillo, Leonardo