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

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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.