Numerical Investigation On Dynamic Characteristics Of Supercooled Large Droplets Impacting And Icing On The Wall

With the discovery and recognition of the Supercooled Large drops（SLD）freezing weather conditions,the damage of Supercooled Large drops to flight safety has been paid more and more attention.Because of the limitation of flight test and ice wind tunnel test,the numerical simulation software is becoming the main tool to study the supercooled water droplet freezing phenomenon,however,because of the complexity of the mechanism of supercooled water droplet freezing,the researchers have not established the accurate water droplet movement model and the water droplet impact model.In this paper,aiming at the existing problems,the phenomenon of single supercooled water droplet impinging on the wall is studied,and a physical model is established to simulate the dynamic behavior of supercooled water droplet impinging on the wall,finally,the effects of various factors on supercooled water droplets impinging on ice are studied.The main contents of this paper are as follows:（1）In this paper,a physical model is established to simulate the dynamic process of supercooled water droplet impinging on the wall,and the commercial software FLUENT is used to simulate the dynamic process of supercooled water droplet impinging on the wall,and the VOF model and enthalpy-porosity model are used,the computational model is built,and the simulation results are compared with the experimental results to verify the accuracy of the numerical simulation tool.（2）In this paper,the selection and setting of the boundary conditions of the computational domain are determined by consulting the meteorological conditions of supercooled water droplets freezing in Appendix O of FAR 25 regulation of airworthiness,and the key parameters needed in the calculation are set and verified,finally,some important parameters,such as A_mush,mesh resolution,contact angle and so on,are defined and used in the simulation.（3）In this paper,the effects of physical properties of water droplets,wall characteristics and air factors on the dynamic process of supercooled water droplets impinging on the wall are studied by numerical simulation method.The effects of various factors on the dynamic process are analyzed in detail.The numerical simulation results show that the main factors affecting the dynamic process of supercooled water droplets impinging on the wall are droplet diameter,droplet velocity and wall contact angle.Water droplet temperature,wall temperature,air temperature and air pressure have limited influence on this process,but they will affect the icing phenomenon from other aspects.（4）In this paper,the impact model of super-hydrophobic inclined wall with contact angle of 150°is established by analyzing the influence of many factors.A key parameter K_SLD is defined to describe the motion state of water droplets after impinging on the wall.It is found that the critical conditions for spreading and splashing of 100μm water droplets are43≤K_{SL D}<50 and for splashing and rebounding areK_{SL D}≥50,and the established impact model is verified.