Lattice Boltzmann Study on the Motion of Dual Droplets in Microchannels With Contact Angle Hysteresis北大核心CSCD

接触角滞后表现为流体在非理想固体表面上运动时前进接触角和后退接触角不同，是两相流体在润湿表面上流动的重要现象.该文采用改进的伪势格子Boltzmann(LB)多组分模型，并与几何润湿边界条件相结合，研究了两个液滴在具有接触角滞后性微通道表面上的运动行为，主要研究了通道内特征数、通道表面性质以及液滴初始参数的影响.研究结果表明：毛细数的增大有助于液滴的移动，然而并不利于液滴的排出，且毛细数的增加对上游液滴的影响大于其对下游液滴的影响；另一方面，接触角滞后性窗口越大，液滴运动和形变更迟缓，但形变程度更明显，两液滴更早地发生合并，但更晚地排出管道；液滴间距的增加使液滴的运动行为在不同阶段表现为不同的模式，但都导致通道中残留小液滴，使得液滴排出通道的时间增加.研究结果还表明：上游液滴和下游液滴的相对尺寸差距越大，越不利于液滴排出管道.

Lattice Boltzmann Study on the Motion of Dual Droplets in Microchannels With Contact Angle Hysteresis

The contact angle hysteresis is defined as the difference between the advancing and receding contact angles, and is an important phenomenon in the two-phase flow on the wet surface. An improved pseudo-potential lattice Boltzmann (LB) multiphase flow model, combined with geometric wetting boundary condition, was employed to study the motion behavior of dual droplets in microchannels with contact angle hysteresis. The effects of the capillary number, the wettability, the contact angle hysteresis window width, the initial distance between the two droplets and the relative size of the droplets on the dynamic behavior of the droplets in the microchannel, were investigated. The research results show that, the increase of the capillary number is conducive to the movement of droplets, but not conducive to the discharge of droplets from the microchannel, and the influence of the capillary number on the upstream droplet is greater than that on the downstream droplet. On the other hand, the larger the contact angle hysteresis window is, the slower the droplet motion and deformation will be, but the more obvious the deformation will be, and the earlier the two droplets will merge but the later they will discharge from the microchannel. In addition, with the increase of the initial distance between the two droplets, the droplet motion mode will differ among different stages, but the duration of the droplet discharge will extend. Correspondingly, the larger the relative size difference between upstream and downstream droplets is, the more difficultly the droplets will discharge from the microchannel.