双液滴同时垂直撞击液膜数值研究

应用数值法对双液滴垂直撞击液膜的动力学行为进行研究.采用VOF法结合网格局部瞬时加密技术捕捉气液两相界面.主要讨论了液滴韦伯数和液滴间距对碰撞演化过程和飞溅特性的影响,给出演化过程中包括二次液滴数量及尺寸等特性参数的变化规律.结果表明,双液滴撞击液膜,除了会生成皇冠形水花外,还会出现水花相撞形成的中心射流.在研究范围内,中心射流产生的二次液滴尺寸比皇冠形水花处生成的液滴尺寸小,中心射流破碎较早,所以二次液滴平均尺寸初始阶段增长较快,后期变化较慢,近似呈现线性增长.

Numerical investigation on two droplets normally onto liquid film

The impingement process of two droplets normally onto a liquid film is investigated by numerical simulations. Gas-liquid interface is captured by the volume of fluid (VOF) method, an adaptive local refinement technique is used to optimize mesh quality. The effects of Weber number and spacing between two droplets on the collision evolution process and splashing characteristics are discussed, and the variations of the number and the size of the secondary droplets are revealed. Experimental results show that two droplets normally impacting on film can produce not only crown spray but also a liquid jet generated by the collision of two crown sprays. Within the scope of the study, the size of the secondary droplets generated from liquid jet is smaller than that in crown spray, and the crush of the liquid jet is earlier. So the average diameter of all the secondary droplets in the space changes fast in the early stage, but slows down in the later stage, showing approximate linear growth trend.