液滴喷射过程中碰撞的形态及流场模拟分析

利用VOF方法建立单个液滴与基板发生碰撞沉积变形的模型,分别对液滴的运动、射流、弛豫和浸润等4个阶段形态变化进行了分析。对模拟结果分析发现:液滴碰撞速度越大,射流能达到的铺展半径越大,液滴最后平衡所用的时间也越长,但速度太大可能导致在浸润阶段液滴回缩时形成中间空缺的现象。模拟结果与照片相符合,说明文中研究方法可行。对液滴铺展达到最大半径、平衡态半径的模拟值和计算值进行比较,二者的误差很小。液滴流场的变化是决定其形态变化的本质,通过对模拟得到的液滴内部流场进行分析,流场变化和液滴4个阶段的形态变化完全一致,从液滴内部掌握了其变形机理。

Simulation of the Shape and Flow Field of a Droplet after Impacting a Substrate

The transformation of droplet shape and flow field after impacting a substrate in spray process is studied in this paper.The deformation model of a single droplet depositing on the substrate was established with the method of volume of fluid(VOF).The distortion of the droplet can be decomposed into four phases: kinetic phase,spreading phase,relaxation phase and wetting phase.The faster the impact velocity of the droplet,the bigger the radius in spreading phase,but a circular vacancy possibly appears if the droplet impact velocity is too fast.The simulative results are in accordance with the CCD photos.The calculated values of the biggest radius and the equilibrium radius conform to those by simulation,and the error is small.The flow field change was analyzed,and it is consistent with the shape change during the four phases.