Understanding the role and use of superhydrophobic coatings for aircraft and powerplant icing

该项目是为期一年的“飞机防冰用超疏水涂层的防冰评估”项目的继续。 所设计的超疏水涂层（SHC）小尺度翼型在防冰和除冰模式下表现出良好的性能。结果表明，对于完全蒸发的情况下，使用SHC翼型提供高达75%的热输入节省。本拟议项目旨在通过数字和实验相结合的研究，将技术准备水平从2提高到4。 由于对液滴/表面相互作用缺乏基本了解，特别是在存在空气剪切流的情况下，因此难以实现适当的涂层开发。拟议的实验/数值研究是从过去的调查不同，它需要一个全面的方法来涂层的问题，不仅从应用程序，制造和结冰特性的角度来看，但也水滴动态表面上。它将特别关注在静态和动态（冲击）条件下与超疏水表面的液滴相互作用。 还将对目前使用的未经处理的铝表面进行调查，以建立基线。最初的研究将集中在使用各种超疏水表面制成的平坦试样的静止液滴的滑动行为。本研究将扩展到研究液滴撞击平坦表面后的滑动行为（即液滴撞击不同疏水性表面的动力学）。除了实验项目外，还将开发一个液滴撞击表面的数值模型，该模型将使用实验研究产生的静态和动态接触角信息来检查表面处理。我们将使用流体体积（VOF）的方法来模拟液-气界面的变形以及凝固和相变。从这些模型研究中学到的原理将应用于翼型的情况，试图为机翼和短舱的超疏水涂层的应用提出建议。此外，将广泛研究SHC的磨损和侵蚀机制，以提高其在紫外线和污垢暴露方面的寿命。

This project is the continuation of a one-year project on "Ice-phobic evaluation of superhydrophobic coatings for aircraft icing protection". The devised superhydrophobic coated (SHC) small scale airfoil showed promising performance in both anti- and de-icing modes. It was demonstrated that for fully evaporative case, using SHC airfoil provides up to 75% savings on heat input. This proposed project is aimed at improving the technology readiness level (TRL) from 2 to 4 through a combined numerical and experimental study. The absence of fundamental understanding of the drop/surface interactions, especially in the presence of an air shear flow, has made it difficult to achieve proper coating development. The proposed experimental/numerical study is different from past investigations in that it takes a comprehensive approach to the issues of coatings, not only from the point of view of application, fabrication and icing characteristics, but also that of water drop dynamics on surfaces. It will specifically focus on drop interactions with superhydrophobic surfaces in static and dynamic (impact) conditions. Untreated aluminum surface currently in use will also be investigated to establish a baseline. Initially the study will focus on sliding behavior of stationary drops using flat coupons made of various superhydrophobic surfaces. This study will be extended to study the sliding behavior of a drop after its impact on the flat surface (i.e. the dynamics of drop impact on surfaces with various hydrophobicities). Alongside the experimental program, a numerical model of a drop impacting on a surface will also be developed which will use the static and dynamic contact angle information generated from experimental studies to examine surface treatments. We will use the proven method of Volume of Fluid (VOF) in order to model the deformation of liquid-gas interface as well as the solidification and phase change. Learned principles from these model studies will be applied to case of an airfoil in an attempt to generate recommendations for application of superhydrophobic coating for wings and nacelles. In addition, wear and erosion mechanisms for SHC will be extensively studied to improve its longevity in terms of UV and dirt exposure.