One of the important aspects in improving the efficiency of electrochemical processes, such as water electrolysis, is the efficient removal of bubbles which evolve from the electrodes. Numerical modelling based on Computational Fluid Dynamics (CFD) can describe the process, provide insights into its complexity, elucidate the underlying mechanisms of how bubbles evolve and their effect as well as aid in developing strategies to reduce the impact of the bubble.

In this paper, a Volume of Fluid (VOF) based simulation framework to study the evolution of hydrogen bubbles in the order of few hundred micrometers, refered to as continuum scale bubbles, is proposed. The framework accounts for the multiphase nature of the process, electrochemical reactions, dissolved gas transport, charge transport, interfacial mass transfer and associated bubble growth. The proposed solver is verified, for two-dimensional cases, by comparison to analytical solution of bubble growth in supersaturated solutions, stationary bubble, rising bubbles and qualitative analysis based on experimental observations of the variations in current based on static simulations. The proposed solver is used to simulate the evolution of a single bubble under various wetting conditions of the electrode as well as the coalescence driven evolution of two bubbles. The results show that as the bubbles detach, its surface oscillates and the shape of the rising bubble is determined by the balance between drag force and surface tension. These surface oscillations, which causes the bubble to get flattened and elongated, results in temporal variation of the electrical current. The reduction of current due to bubble growth is visible only when these surface oscillations have reduced. The simulations also show the current as a function of the position of the bubble in the interelectrode gap. The framework also predicts the increase in current as a result of bubbles leaving the surface which is larger when the process is coalescence driven. The simulations indicate that bubble coalescence is the underlying mechanism for continuum scale bubble detachment.

提高电化学过程（例如水电解）效率的重要方面之一是有效去除电极上产生的气泡。基于计算流体动力学 (CFD) 的数值建模可以描述该过程，深入了解其复杂性，阐明气泡如何演变及其影响的潜在机制，并有助于制定减少气泡影响的策略。

在本文中，提出了一种基于流体体积 (VOF) 的模拟框架，用于研究数百微米量级的氢气泡（称为连续尺度气泡）的演化。该框架解释了该过程的多相性质、电化学反应、溶解气体传输、电荷传输、界面传质和相关气泡生长。在二维情况下，通过与过饱和溶液中气泡生长的解析解、静止气泡、上升气泡和基于静态模拟的电流变化实验观察的定性分析进行比较，验证了所提出的求解器。所提出的求解器用于模拟在电极的各种润湿条件下单个气泡的演化以及两个气泡的聚结驱动演化。结果表明，当气泡脱离时，其表面发生振荡，上升气泡的形状由阻力和表面张力之间的平衡决定。这些导致气泡变平和拉长的表面振荡导致电流的时间变化。只有当这些表面振荡减少时，才能看到由于气泡增长导致的电流减少。模拟还显示电流是电极间间隙中气泡位置的函数。该框架还预测了由于气泡离开表面而导致的电流增加，当该过程受到聚结驱动时，该电流会更大。模拟表明气泡聚结是连续尺度气泡脱离的潜在机制。