Detachment Dynamics Induced by Unequal Microbubble Coalescence*

Understanding the dynamics of microbubble detachment is critical in various engineering systems, such as the design of micro gas generator to reduce the inefficiency of reaction, self-cleaning in the microchannel, and thermal management of semiconductor products, to name a few. In this work, we numerically study the behavior of coalescence-induced detachment of unequal size microbubbles on a flat rigid wall using a free-energy approach based on lattice Boltzmann method. The reliability of the triple-phase (solid, liquid, and gas) lattice Boltzmann model is validated through comparisons with analytical and experimental results of bubble coalescence on the solid surface. From systematic simulation and analysis by varying the bubble size ratio, contact angle, and height of the channel, we reveal the detachment mechanics induced by unequal microbubble coalescence and seek for an optimal design to detach bubbles in micro-channel. It is found that the detachment of the bubble is easier to occur when the solid phase with super hydrophilic material and the bubble size ratio is close to 1.