单液滴撞击薄液膜产生二次雾化过程的数值模拟

应用数值模拟方法研究单液滴撞击薄液膜的动力学行为.在二维轴对称坐标系内,采用VOF方法与网格局部瞬时加密技术相结合,跟踪液滴和液膜与空气间的气液两相界面.结果表明,液滴撞击薄液膜的演化行为主要受液滴初始动能、表面张力以及液体黏性的影响.初始动能越大,则形成的空间液膜最大高度越大,达到稳定状态越晚,飞溅开始时刻越早,飞溅生成的二次液滴数量也越多;在扩展后期及回缩阶段,空间液膜的形成主要受液体黏度影响,增加液体黏度会阻碍空间液膜飞溅;表面张力增大,形成的空间液膜高度减小、厚度增加,同时阻碍二次液滴的生成.

Numerical Simulation of Secondary Atomization on Impacting of a Droplet upon a Thin Liquid Film

The collision dynamics between a droplet and a thin liquid film has been studied by numerical simulation.The full Navier-Stokes equations are solved in an axisymmetric formulation coupled with the volume-of fluid(VOF)method.The surface tension force is modeled by a continuum surface force model.An adapting local re-finement technique is utilized to provide fine grid for tracking the interface between the gas and the liquid,including the shapes of the droplet and liquid film.Results indicate that the motion behavior of the droplet impingement upon the thin film is dominantly influenced by initial kinetic energy,surface tension and liquid viscosity.The greater the initial kinetic energy is,the higher the height of the crown generated by impacting is,the later the steady state is reached,the earlier the splashing takes place,and the more secondary droplets are produced from the crown.Viscos-ity influences the crown behavior mainly at the later stage of crown spreading and in retraction process.Increasing viscosity leads to a delay in crown splash.High surface tension appears to reduce crown height and retard the produc-tion and evolution of secondary droplets from the rim of the crown.