CFD – PBM simulation of surfactant effects in bubble columns: Coalescence modeling based on critical velocity

Abstract Quantifying surfactant effects in bubble columns remains challenging. The difficulty lies in linking local interfacial phenomena, such as bubble deformation and liquid‐film drainage, to macro‐scale hydrodynamics. In our previous study (Liu et al., AIChE J . 2025; 71 (10):e18902), the Marrucci number (Ma)—the ratio of resistance induced by surface tension gradients to the driving force during liquid film drainage—was identified as a key parameter for quantifying surfactant effects, and a critical velocity correlation was developed based on bubble coalescence experiments. In this work, the critical velocity model was incorporated into the coalescence kernel within the PBM framework, and the CFD–PBM simulations reproduced the Sauter mean diameter () observed in experiments for various ethanol concentrations. Additional simulations in propanol solutions further demonstrate the model's applicability by capturing the distinct interfacial effects of different surfactants. These findings show the model's potential to reflect surfactant effects in macro‐scale fluid dynamics.