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

过冷大水滴 (SLD)，包括冻毛毛雨和冻雨滴，比大多数飞行中飞机结冰事故中涉及的云大小水滴大 100 倍。 当 SLD 撞击机身表面时，它们通常会影响当前防冰/除冰系统保护范围之外的区域，并溅入二次液滴，洒落在未受保护的区域。 这会导致地表水回流和不受控制的积冰。 由于 SLD 导致的飞机结冰发生的频率比最初想象的要高，现在被认为是一种重大危险。该合作研究项目将结合实验和建模来了解SLD结冰现象的基本物理原理，以便实施有效的防/除冰措施，确保飞机在寒冷天气下更安全、更高效地运行。 该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。 该项目将培训研究生和本科生进行研究，并将开发教育工具，激励高中生，特别是来自 STEM 领域代表性不足的群体的高中生，继续进行科学和工程研究。这项合作研究的总体目标是进行综合理论、数值和实验研究，以量化与 SLD 结冰现象相关的重要微观物理过程，如液滴撞击、反弹、飞溅、地表水回流和积冰。 研究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、更高效地运行。研究任务包括：1）开发基于经过验证的多相流求解器和新颖的流体界面矩表示方法的SLD结冰模拟工具； 2）进行理论、实验和数值研究，以表征与SLD结冰相关的干湿表面上的液滴撞击、反弹和飞溅特征，以开发液滴撞击模型，该模型全面考虑了先前研究中忽略的控制因素； 3) 进行综合数值和实验研究，以检验地表水回流的特征及其对 SLD 结冰的影响。 该研究计划将通过添加新的教学模块和创建新的课件来融入本科生和研究生课程中以激发学生的兴趣？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来从事拟议的研究，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.