固体壁面上气泡聚并后的微对流质量传递
Micro-convection mass transfer following bubble coalescence on a solid wall
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中文总结 AI 辅助
利用Basilisk流体体积法模拟固体壁面气泡聚并跳离后的微对流质量传递，发现高施密特数下核心区域舍伍德数局部增强且持续，增强因子依赖边界层厚度，微对流影响略强于纯浮力情形。
中文摘要 AI 辅助
采用Basilisk流动求解器中的流体体积法（Volume-of-Fluid）研究了固体基底上气泡聚并诱导跳离后的质量传递，涉及四种气泡半径（$R_m=150$和25 $\mu$m，氢-水物性）与施密特数（$\text{Sc}=210$和1）的组合。结果表明，在聚并时刻后约0.5至1个惯性-毛细时间单位内，气泡界面的快速运动引发了低浓度液体的相对较强的向下夹带。在$\text{Sc}=210$时，这导致合并气泡南极下方核心区域（半径约为$R_m/2$的区域）的舍伍德数出现高度局部增加，且由于大$\text{Sc}$下的缓慢扩散，该增加在气泡脱离后持续较长时间。舍伍德数的增强因子高度依赖于聚并时刻质量传递边界层的状态，随边界层厚度减小而增大。跳离后不久，气泡速度显著衰减，并迅速接近其自由上升终端速度。在此阶段，微对流对壁面传质系数的影响在孤立考虑时并不显著，与文献中关于纯浮力驱动气泡上升的报道类似——但略强一些。
英文摘要
The Volume-of-Fluid implementation in the \href{basilisk.fr}{Basilisk} flow solver is employed to study mass transfer after coalescence-induced jump-off of bubbles on solid substrates at four combinations of bubble radius ($R_m=150$ and 25 $μ$m, hydrogen-water properties) and Schmidt number ($\text{Sc}=210$ and 1). The results show a relatively strong downward entrainment of low-concentration liquid, induced by a rapid movement of the bubble interface at approximately 0.5 to 1 inertio-capillary time units after the moment of coalescence. At $\text{Sc}=210$, this leads to a highly local increase of the Sherwood number at a core region (roughly an area of radius $R_m/2$) below the south pole of the merged bubble, which persists long after the bubble departure due to the slow diffusion at large $\text{Sc}$. The enhancement factor of the Sherwood number is highly dependent on the state of the mass-transfer boundary layer at the moment of coalescence, increasing with smaller boundary layer thicknesses. Shortly after the jump-off, the velocity of the bubble is considerably damped and rapidly approaches its free-rise terminal velocity. The effect of micro-convection on the wall mass transfer coefficient at this stage is insignificant when isolated, similar to what is reported in the literature for purely buoyancy-driven bubble rise -- but slightly stronger.
