液滴撞击湿润壁面的运动形态及飞溅运动机制

MOVEMENT AND SPLASHING OF A DROPLET IMPACTING ON A WET WALL

壁面液体层的存在对液滴撞击壁面的运动具有重要的影响.采用气液两相流动相界面追踪的水平集和流体体积复合方法和壁面润湿模型,实现了液滴撞击湿润壁面运动的数值求解;在此基础上,开展了液滴撞击湿润壁面运动的研究.研究结果表明:液滴以不同速度撞击湿润壁面时,会呈现出黏附铺展、波动运动、皇冠几何体运动以及飞溅运动等几种不同的运动形态,液滴撞击湿润壁面后的压力分布是不同运动形态形成的主要原因;飞溅运动是一定条件下皇冠几何体运动的一种特殊形态,液滴从皇冠几何体侧壁顶端的飞溅分离满足毛细破碎理论;撞击速度对分离液滴的运动方向影响较小,而对壁面液体层厚度的影响则较大;撞击速度和壁面液体层厚度对分离液滴形态、飞溅分离位置、飞溅速度以及飞溅发生时刻等都具有一定的影响.

The liquid layer has an important effect on the movement of a droplet after impacting on a wet wall. The numerical solution of the movement of a droplet impacting on a wet wall was realized by using the combined Level Set- VOF method for gas-liquid interface tracking and the wall wetting model, and the movement of a droplet impacting on a wet wall was researched. The results show that there are several different movement forms after a droplet impacting on a wet wall under different impacting velocities, such as adhesion spreading, wave, crown and splashing, and the pressure distribution induced by the impacting is the main reason of different movement forms. The movement of splashing is a special form of crown movement under certain conditions, and its formation satisfies the theory of capillary breaking. The effect of the impacting velocity on the movement direction of splashing is small, while the effect of the thickness of the liquid layer is bigger. Both impacting velocity and liquid layer have certain influence on the droplet shape, splashing separation position, splashing velocity and splashing occurrence time.