Towards a model for splashing: An experimental program to analyze a splash in terms of its jets

许多工业和自然过程在很大程度上依赖于飞溅，即液滴与表面的碰撞以及随后破碎成更小液滴的过程。常见但重要的例子包括喷墨打印、喷漆、喷雾冷却、微电子产品的精密焊接、农药喷洒、灭火、种子、细菌和病毒的空气传播。我们预测和控制这些现象的能力受到对支配这些现象的基本过程--飞溅--的不完全理解的限制。这一提议的首要目标是利用一种新开发的技术对飞溅进行基础研究，该技术使以前所未有的空间和时间分辨率测量飞溅的流体动力学成为可能。该项目包括一个重要的教育部分，包括在本科生和研究生一级培训未来的科学家，向K-12社区中没有代表性的少数群体进行宣传，以及通过社交媒体和与博物馆的合作向公众传播科学。喷流是液滴撞击后很快产生的高速液体薄片。这些目标将通过(1)测量射流的早期动力学和稳定性，(2)确定定性不同动力学的分叉点，(3)测量最不稳定的波长和由此产生的液滴分布，(4)对射流的稳定性进行建模并与实验进行比较，(5)研究从装置中产生的射流，该装置消除了液滴碰撞中的飞溅。实验将利用高速X射线和可见光成像技术，在不同液体和气体组合的撞击速度范围内记录液气界面的演变和飞溅过程中产生的液滴的尺寸分布。这些数据将由直接的数值模拟加以补充。该计划预计将(1)产生最高分辨率的飞溅实验特征，(2)测试飞溅可以根据喷嘴进行分析的假设，以及(3)为建立涉及拓扑变化的更复杂过程的建模提供基本基础。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。

Many industrial and natural processes depend crucially on splashing, the collision of a liquid drop with a surface and its subsequent fragmentation into smaller droplets. Common yet important examples include inkjet printing, spray painting, spray cooling, precision soldering of microelectronics, pesticide spraying, fire suppression, airborne dispersal of seeds, bacteria, and viruses. Our ability to predict and control such phenomena is limited by an incomplete understanding of the fundamental process that governs these phenomena, the splash. The overarching goal of this proposal is a fundamental study of splashing using a newly-developed technique that makes it possible to measure the fluid dynamics of a splash with unprecedented spatial and temporal resolution. The project includes a significant educational component, including training of future scientist at the undergraduate and graduate level, outreach to unrepresented minorities in the K-12 community, and dissemination of science to the public through social media and collaborations with museums.The goal of this project is to develop a model of splashing by decomposing the splash in terms of jets. Jets are the high-speed sheets of liquid produced soon after drop impact. The objectives will be met by (1) measuring the jet's early time dynamics and stability, (2) determining the bifurcation points for qualitatively different dynamics, (3) measuring the most unstable wavelength and the resulting droplet distribution, (4) modeling the stability of jets and comparing with experiments, (5) studying jet production from an apparatus that removes the complications in splashing from drop impact. Experiments will record the evolution of the liquid-gas interface and the size distribution of droplets created during the splash using high speed X-ray and visible light imaging for a range of impact speeds with different liquid and gas combinations. These data will be supplemented with direct numerical simulations. This program is expected to (1) produce the highest resolution experimental characterization of splashing, (2) test the hypothesis that splashes can be analyzed in terms of jets, and (3) provide a fundamental basis for modelling more complicated process that involve changes of topology.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.