不同润湿性表面固着双液滴蒸发过程LBM数值模拟

LBM Numerical Simulation of Sessile Paired Droplets Evaporation on Different Wettability Surfaces

摘要: 阵列液滴蒸发在蛋白质及核酸生物打印及胶体液滴蒸发自组装领域有重要应用。本文采用格子Boltzmann方法模拟了固着基板上双液滴的蒸发过程，研究了基板润湿性及液滴间距对双液滴蒸发过程的影响，模拟结果与文献中实验结果吻合良好。研究结果表明，双液滴在加热基板上蒸发时发生铺展合并现象是由基板润湿性及液滴间初始放置间距共同决定的。当出现合并现象时，液滴合并后以单液滴形态进行蒸发，其蒸发寿命远大于未发生合并现象时的液滴蒸发寿命。当未发生合并现象时，受液滴间有限空间抑制，液滴面向大空间一侧的蒸发速率大于液滴相邻侧；液滴为了维持球形形态，内部产生了向蒸发速率较快一侧输运流体的微流动，导致液滴左右两侧接触线收缩不对称，产生液滴中心外迁现象。与单液滴蒸发状态相比，成对液滴蒸发寿命比单液滴蒸发时延长，但小于发生合并后的蒸发寿命。论文通过大量模拟，获得了通过基板润湿性及液滴间距判断液滴蒸发过程是否合并的判据。

Abstract: Array droplets evaporation has important applications in the fields of protein and nucleic acid bioprinting and colloidal droplet evaporation self-assembly. In this paper, the lattice Boltzmann method is used to simulate the evaporation process of paired droplets on a sessile substrate, and the influence of substrate wettability and droplet spacing on the paired droplets evaporation pro-cess was studied. The simulation results are in good agreement with the experimental results in the literatures. The research results show that the phenomenon of spreading and merging of paired droplets when they evaporate on the heated substrate is determined by the wettability of the substrate and the initial spacing between the droplets. When the merging phenomenon occurs, these droplets are merged to evaporate in the form of a single droplet, and the evaporation life of the droplet is much longer than that when the merging phenomenon does not occur. When there is no merging phenomenon, restrained by the limited space between the droplets, the evaporation rate of the droplet facing the large space is greater than that of the adjacent side of the droplet; in order to maintain the spherical shape of the droplet, there is an internal transfer to the faster evaporation rate. The micro-flow of the transport fluid causes the contact lines on the left and right sides of the droplet to contract asymmetrically, resulting in the phenomenon of the center of the droplet moving out. Compared with the single droplet evaporation state, the evaporation life of the paired droplets is longer than that of the single droplet evaporation, but is shorter than the evaporation life after merging. Through a large number of simulations, the paper obtained the criterion for judging whether the droplet evaporation process is merged by the wettability of the substrate and the droplet spacing.