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

过冷大液滴(SLD)，包括冻结的毛毛雨和冻结的雨滴，比大多数飞行中飞机结冰事件中涉及的云大小的液滴大100倍。当SLD撞击机身表面时，它们往往会影响到当前防冰/除冰系统保护之外的区域，并溅起二次液滴，洒在未受保护的区域。这会导致地表水流失和不受控制的结冰。低密度脂蛋白导致的飞机结冰比最初认为的更频繁，现在被认为是一种重大危险。这一合作研究项目将结合实验和建模，以了解SLD结冰现象的基本物理，以便实施有效的防冰/除冰措施，以确保飞机在寒冷天气下更安全、更高效地运行。研究团队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。该项目将培训研究生和本科生进行研究，并将开发教育工具，以激励高中生，特别是那些来自STEM领域代表性不足的群体的高中生继续学习科学和工程。这项合作研究的总体目标是进行一项综合的理论、数值和实验研究，以量化与SLD结冰现象有关的重要微观物理过程，如液滴撞击、反弹、飞溅、地表水回流和结冰。结果将提高我们对飞机在大气结冰条件下更安全、更有效地运行的潜在物理学的理解。研究任务包括：1)基于一种新的流体界面矩表示方法开发了一种基于多相流求解的SLD结冰模拟工具；2)开展了理论、实验和数值研究，以表征SLD结冰过程中液滴在干、湿表面上的撞击、反弹和飞溅，从而建立了液滴冲击模型，该模型综合考虑了以往研究中忽略的控制因素；以及3)进行了一体化的数值和实验研究，以考察地表水的回流特性及其对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来激励学生，从而纳入本科和研究生课程。对热流体科学的兴趣。来自代表性不足群体的学生将被主动招募参与拟议的研究，以促进对科学和工程的参与。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。

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.