考虑滞后效应的过冷水滴撞击冻结过程模拟

Simulation of impacting-freezing process of supercooled water droplet considering hysteresis effect

为深入理解船舶上层建筑结构表面细观结冰现象及机理,建立了考虑过冷度和动态接触角影响的单个过冷水滴撞击冷壁面后冻结过程数值模型.该模型基于Fortran编程语言,采用焓-孔隙度相变方法和耦合流体体积法(VOF)与水平集法(level-set)的VOSET气液界面追踪方法,同时追踪了固-液和气-液两种界面,并实现了气-液-固三相的统一显示,模拟结果与相关实验结果一致.选用的Kistler动态接触角模型能够在较大接触线速度范围内(如-8~12 m/s)保持较高准确性.进一步探讨了水滴过冷度、表面接触角及初始速度对水滴撞击及冻结过程的影响,结果表明:表面接触角越小,过冷度越大,会导致水滴冻结速率增大,并且水滴最大铺展直径与初始速度成正比.

In order to deeply understand the meso phenomenon and mechanism of the ship superstructure surface icing,a numerical model considering the effects of supercooling and dynamic contact angle was established,which can simulate the freezing process of a single supercooled droplet impacting the cold surface.The model was based on Fortran programming language.The enthalpyporosity phase change method and the VOSET gas-liquid interface tracking method coupled with the volume of fluid(VOF)method and level-set method were used to capture the gas-liquid and solid-liquid interfaces at the same time.The simulation results can display the gas-liquid-solid three-phase uniformly,and are consistent with the relevant experimental data.The Kistler dynamic contact angle model selected can maintain high accuracy in a large contact line velocity range(such as-8-12 m/s).The effects of droplet supercooling,surface contact angle and initial velocity on the impacting-freezing process were further discussed.The analysis shows that the smaller surface contact angle and the greater supercooling increase the freezing rate of the water droplet,and the maximum spreading diameter is directly proportional to the initial velocity of the water droplet.