Breakup dynamics of viscous bubbles in heart-shaped microchannel: Mechanisms and predictive models

To enhance the gas–liquid mass transfer efficiency in high-viscosity fluids within heart-shaped microchannels, this study systematically investigated the bubble breakup dynamics at the arc-shaped junction of heart-shaped microchannel under different viscosities of glycerol solution. High-speed camera observed that bubble breakup at the arc-shaped junction could be divided into three cases: breakup with obstruction, breakup with tunnel, and squeezing breakup. The occurrence of bubble breakup is related to the bubble equivalent length (l₀/w₀) and the capillary number (Ca), and the bubble breakup pattern transition rule under different liquid phase viscosities was obtained through data analysis. Furthermore, the effects of the bubble equivalent length, total capillary number, liquid phase viscosity (μ_L), and velocity of the rear-bubble (U_g) on bubble squeezing breakup were investigated. The data analysis showed that U_g significantly affected the power-law indices α and β, increasing α by 23.8 % and β by 43.9 %, respectively. In addition, this study proposed a three-dimensional surface model l₀/w₀ = a(U_g/U_in)^bCa^c for the first time to predict whether bubble squeezing breakup occurs, offering a robust theoretical framework for controlling bubble breakup in high-viscosity systems. This study deepens the understanding of bubble breakup dynamics in high-viscosity systems and provides a theoretical foundation for structural optimization of heart-shaped microchannels.