Collaborative Research: A fundamental study on supercooled large droplets: impacting, splashing, surface water dynamics, and ice accretion

包括冻雨和冻雨在内的过冷大液滴（SLDs）比大多数飞机结冰事故中涉及的云大小的液滴大100倍。当SLDs撞击机身表面时，它们通常会撞击到当前防冰/除冰系统保护范围之外的区域，并飞溅成二次液滴，洒在未受保护的区域。这导致了地表水的倒流和不受控制的冰的增加。由于SLDs导致的飞机结冰比最初想象的要频繁，现在被认为是一个重大的危险。该合作研究项目将结合实验和建模来了解SLD结冰现象的潜在物理特性，以便实施有效的防冰/除冰措施，以确保飞机在寒冷天气中更安全、更高效地运行。研究小组将与其他政府机构和航空航天公司的科学家合作，进一步扩大研究的影响。该项目将对研究生和本科生进行研究培训，并开发教育工具，以激励高中生，特别是那些在STEM领域代表性不足的群体，继续从事科学和工程研究。本合作研究的总体目标是开展理论、数值和实验相结合的研究，量化与SLD结冰现象相关的重要微物理过程，如液滴撞击、反弹、飞溅、地表水倒流和冰的增加。结果将提高我们对基础物理的理解，使飞机在大气结冰条件下更安全、更有效地运行。研究任务包括：1)基于验证的多相流求解器和新颖的流体矩界面表示方法，开发SLD结冰仿真工具；2)通过理论、实验和数值研究，对液滴在与SLD结冰相关的干湿表面上的撞击、反弹和飞溅进行表征，建立综合考虑以往研究忽略的控制因素的液滴撞击模型；3)采用数值与实验相结合的方法，研究地表水径流特征及其对SLD结冰的影响。该研究项目将通过增加新的教学模块和制作新的课件，纳入本科和研究生课程，以激发学生的兴趣。对热流体科学感兴趣。来自代表性不足群体的学生将被积极招募参与拟议的研究，以促进科学和工程的参与。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Supercooled large droplets (SLDs), which include freezing drizzle drops and freezing raindrops, are up to 100 times larger than the cloud-sized droplets that are involved in most in-flight aircraft icing incidents. When SLDs impinge on airframe surfaces, they often impact on regions beyond the protection of current anti-/de-icing systems and splash into secondary droplets that sprinkle unprotected areas. This causes surface water runback and uncontrolled ice accretion. Aircraft icing due to SLDs, which occurs more frequently than first thought, is now recognized as a significant hazard. This collaborative research project will use a combination of experiments and modeling to understand underlying physics of SLD icing phenomena so that effective anti-/de-icing measures can be implemented to ensure safer and more efficient operation of aircraft in cold weather. The research team will collaborate scientists at other government agencies and aerospace companies to further broaden the impacts of the research. The project will train graduate and undergraduate students in research and will develop educational tools that will inspire high school students, especially those from groups underrepresented in STEM fields, to continue in science and engineering studies.The overall goal of this collaborative research is to conduct an integrated theoretical, numerical and experimental research to quantify important micro-physical processes, such as droplet impact, rebounding, splashing, surface water runback, and ice accretion, that are pertinent to SLD icing phenomena. Results will improve our understanding of the underlying physics for safer and more efficient operation of aircraft in atmospheric icing conditions. The research tasks include: 1) develop an SLD icing simulation tool based on a validated multiphase flow solver with a novel moment of fluid interface representation method; 2) conduct theoretical, experimental and numerical studies to characterize droplet impinging, rebounding and splashing on dry and wet surfaces pertinent to SLD icing to develop droplet impact models that contain a comprehensive consideration of controlling factors ignored in previous studies; and 3) perform an integrated numerical and experimental investigation to examine the characteristics of surface water runback and its effects on SLD icing. The research program will be incorporated into undergraduate and graduate curricula by adding a new teaching module and creating new courseware to stimulate students? interests in thermal-fluid sciences. Students from underrepresented groups will be recruited proactively to work on the proposed research to promote participation in science and engineering.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.