分叉微通道内液滴动力学行为的格子Boltzmann方法模拟  

Lattice Boltzmann simulation of droplet dynamics in a bifurcating micro-channel

作　　者：梁宏[1] 柴振华[2,3] 施保昌[2,3] 

机构地区：[1]杭州电子科技大学物理系,杭州310018 [2]华中科技大学数学与统计学院,武汉430074 [3]华中科技大学煤燃烧国家重点实验室,武汉430074

出　　处：《物理学报》2016年第20期139-148,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11602075;51576079;11272132)资助的课题~~

摘　　要：本文采用格子Boltzmann方法模拟了液滴在分叉微通道中的迁移过程,主要分析壁面润湿性、毛细数、出口流量比对液滴动力学行为的影响机制.结果表明:当毛细数足够大时,液滴在支通道的迁移行为与壁面润湿性密切相关,对疏水壁面,液滴在主通道发生破裂生成两个子液滴,子液滴完全悬浮在支通道中并流向出口.而对亲水壁面,液滴首先同样破裂成两个子液滴,不同于疏水情形,子液滴紧接着发生二次破裂,导致部分二次子液滴黏附在固体表面上,另一部分流向出口;当毛细数足够小时,液滴则滞留在分叉口处,不发生破裂.最后,还发现通过调节出口流量比可以使液滴发生非对称破裂或者不破裂完全从流速较大的支通道流出.The droplet dynamic in a bifurcating micro-channel, as one of the basic multiphase problems, is frequently encountered in the fields of science and engineering. Due to its great relevance to many important applications and also its fascinating physical phenomena, it has attracted the increasing attention in the past decades. However, this problem is still not fully understood since it is very complicated： the droplet behaviors may be influenced by several physical factors. To clearly elucidate the physics governing droplet dynamics in a bifurcating micro-channel, a detailed numerical study on this problem is conducted. The present investigation is based on our recently developed phase-field-based lattice Boltzmann multiphase model, in which one distribution function is used to solve the Cahn-Hilliard equation,and the other is adopted to solve the Navier-Stokes equations. In this paper, we mainly focus on the effects of the surface wettability, capillary number and outlet flux ratio on the droplet dynamics, and the volume of the generated daughter droplet is also presented. The numerical results show that when the capillary number is large enough, the droplet behaviors depend critically on surface wettability. For the nonwetting case, the main droplet breaks up into two daughter droplets, which then completely suspend in the branched channels and flow towards the outlet. While for the wetting case, the main droplet also breaks up into two daughter droplets at first, and then different behaviors can be observed. The daughter droplet undergoes a secondary breakup, which results in part of droplet adhering to the wall,and the remaining flowing to the outlet. The volume of the generated daughter droplet is also measured, and it is shown that it increases linearly with contact angle increasing. When the capillary number is small enough, the droplet remains at the bifurcating position, which does not break up. Finally, we also find that the outlet flux ratio affects the rupture mechanism of the droplet. When the outle

关 键 词：格子BOLTZMANN方法 液滴 微通道 

分 类 号：O35[理学—流体力学]