Numerical simulation of Taylor bubble formation in a microchannel with a converging shape mixing junction

The bubble formation in a square microchannel with a converging shape mixing junction has been simulated under Taylor flow using two different interface capturing methods implemented in ANSYS FLUENT (ANSYS Inc., USA): Volume of Fluid (VOF) method, and coupled Level Set and VOF (CLSVOF) method. Compared with VOF method, CLSVOF method can yield a more accurate gas–liquid interface especially at the rupture stage of the emerging bubble and the obtained bubbles are more consistent with the experimental results. The effect of the contact angle (θ), surface tensions (σ) and liquid viscosity (μL) on the Taylor bubble details (i.e., length, volume and shape) has been investigated systematically. For the highest surface tension (σ = 0.09 N/m) and the highest liquid viscosity (μL = 9.83 mPa s) investigated, the bubble length decreases substantially with an increase of the contact angle as a result of the combined effect caused by the bubble end shape change from convex to concave and the volume decrease of the liquid film surrounding the bubble body. However, the bubble volume is almost constant regardless of the contact angle, which is mainly caused by the difference in bubble shapes. Both the contact angle and the liquid viscosity have an appreciable influence on the bubble shape whereas the influence of surface tension is minor.