过冷大水滴结冰试验相似准则研究

Supercooled Large Droplets (SLD) are commonly referred to the water droplets with the diameter larger than 50 microns. Ice accretion due to SLD is very different from which due to small-diameter water droplets. One of the typical reason is the effects of dynamic process of large droplets, such as the breakup and splashing phenomena and so on. Another reason is that the characteristics of heat and mass transfer during SLD icing are different from those of small water droplets icing, and there is a non-linear thermodynamic process during SLD icing. As a result, the icing test scaling law based on small supercooled water droplets can't be used in the test of SLD icing. In the present project, the scaling law of SLD icing test will be systematically investigated, and a combination method of theoretical analysis, numerical calculation and icing wind tunnel test will be adopted in the study. The goal of the project is to propose a SLD icing scaling law, which is rational and can be used in icing wind tunnel test as the theoretic basis for the selection of test parameters. The main work includes four parts: (1) The investigation into the physics process of SLD icing. (2) The abstraction of the similar parameters. (3) The construction of a SLD icing scaling law and the method for calculating icing test parameters. (4) The Evaluation, validation and application of the SLD icing scaling law. The research is based on the study of physical mechanism of SLD icing. It includes not only fundamental research such as mathematical modeling, formula derivation, but also applied research such as icing calculation and selection of icing test parameters. The results and progress of the work can be directly applied to the engineering requirements of icing wind tunnel test, which indicates the achievements of the current project have great value of science as well as good potentials of being used in engineering.

过冷大水滴（简称SLD）泛指直径大于50微米的过冷水滴。由于SLD结冰耦合了水滴变形、破碎、飞溅等动力学过程以及传质、传热和相变的非线性热力学过程，导致现有的小水滴结冰试验相似准则不再适用于SLD结冰试验。本项目将采用理论分析、数值计算和结冰风洞实验相结合的手段，对SLD结冰过程进行系统研究和分析，目的是掌握SLD结冰试验相似准则的基础理论，建立一套科学、合理的SLD结冰试验相似准则，为结冰风洞试验提供理论指导和参数选取依据。主要研究内容有：（1）SLD结冰基本物理过程的研究与建模；（2）相似参数的提炼及影响规律；（3）相似准则的构建及试验参数的计算方法；（4）相似准则的评估、验证和应用。本项目的研究基于SLD结冰的物理机理，既有数理建模、公式推导等基础性研究，又有结冰预测、结冰风洞试验参数选取等应用性研究，研究成果可直接满足结冰风洞试验的工程需求，具有重要的学术研究价值和工程应用前景。

由于SLD结冰耦合了水滴变形、破碎、飞溅等动力学过程以及传质、传热和相变的非线性热力学过程，导致现有的小水滴结冰试验相似准则不再适用于SLD结冰试验。本项目采用理论分析、数值计算和结冰风洞实验相结合的手段，对SLD结冰试验的相似准则开展了系统研究，主要完成了以下四方面的工作：（1）SLD结冰基本物理过程的研究与建模；（2）相似参数的提炼及影响规律；（3）相似准则的构建及试验参数的计算方法；（4）相似准则的评估、验证和应用。通过以上研究工作，对SLD结冰的机理和动态结冰的特性有了更深入的认识，建立了考虑SLD水滴动力学特性以及相变非平衡特性的相似准则，完成了相似准则的结冰风洞试验验证和应用，在完成以上研究内容的同时，进一步发展了结冰数值计算的方法及工具、形成了相关实验技术。课题发表论文21篇，授权（受理）国家发明专利10项，相关成果的应用获2018年军队科技进步二等奖。这些研究成果为开展大型结冰风洞SLD结冰试验提供了理论依据和技术支撑，也为下一步进行更深入的结冰基础科学问题探索和工程应用奠定了良好基础。