脉冲激光冲击液滴变形和破裂的数值仿真  

Numerical Simulation on Deformation and Rupture of Liquid Droplet Impacted by Pulsed Laser

作　　者：文洲 陆健[1] 张宏超[1] 唐懋 Wen Zhou;Lu Jian;Zhang Hongchao;Tang Mao(School of Science,Nanjing University of Science and Technology,Nanjing 210094,Jiangsu,China)

机构地区：[1]南京理工大学理学院,江苏南京210094

出　　处：《中国激光》2022年第22期107-114,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(11774176)。

摘　　要：通过建立激光与液滴相互作用的物理模型,采用数值仿真研究了激光冲击液滴形成的速度场对液滴变形和流动的影响规律。使用流体体积法,结合层流模型,确定了变形的主要特征和流动的精确细节。结果表明,液滴变形过程和破裂时间与已报道的实验结果有很好的一致性。同时,利用Rayleigh--Taylor不稳定性分析,确定了液滴形变、破裂时间与韦伯数的依赖关系。当韦伯数低于110.7时,液滴向前推进,不会发生整体破碎;韦伯数越高,液滴形变越剧烈,且液滴破裂的碎片越小。另外,液滴破碎后,由于涡量的作用,细小液滴出现自旋、融合、破裂等有趣的现象。Objective Droplet fragmentation is a common natural phenomenon. The study on droplet deformation and rupture caused by pulsed laser impact has not only theoretical importance in fluid mechanics but also practical application value in industrial fields. In the field of extreme ultraviolet nanolithography, it is required to understand the dynamic response of droplets to laser pulse impact to optimize the laser-produced plasma light sources. A laser-induced phase change is a method for moving liquids by optical radiation, allowing for large deformations and flow speeds. In this process, the speed distribution generated by the pulse within the droplet is a crucial factor influencing the droplet deformation and fragmentation. However, less attention has been paid to this speed distribution. Here, the effect of speed field formed by laser impacting droplets on droplet deformation and propulsion is mainly studied.Methods Based on a physical model of the interaction between the laser and the droplet, numerical simulation is employed to investigate the influence of speed fields formed under various laser energies on the droplet deformation and propulsion. Employing the volume of fluid approach, combined with the laminar flow model, the primary characteristics of deformation and the precise details of flow are determined. The pressure implicit with the splitting of operators is employed to solve the problem. The pressure staggering option discretization scheme for pressure is employed. The pressure staggering option discretization gives more accurate findings since interpolation errors and pressure gradient assumptions on boundaries are avoided. For cases with strong surface tension and a high density ratio, this scheme works better. The momentum is discretized by employing the second-order upwind scheme and the volume fraction equation is discretized by the geometric reconstruction scheme. Meanwhile, a Rayleigh--Taylor instability analysis is performed to estimate the dependences of droplet deformation and breakup time on

关 键 词：激光技术 脉冲激光 液滴破碎 表面不稳定性 流体体积 极紫外光刻 

分 类 号：TN249[电子电信—物理电子学]