Flow focusing in microchannels

A volume-of-fluid numerical method is used to predict the dynamics of drop formation in an axi-symmetric microfluidic flow-focusing geometry for a liquid-liquid system. The Reynolds numbers and Weber numbers approximate those of a three-dimensional flow in recently published experiments. We compare the predicted drop formation with the experimental results at various flow rates, and discuss the mechanisms of drop formation in this context. Despite the differences in geometry, we find qualitative correspondence between the numerical and experimental results. Both end-pinching and capillary-wave instability are important for droplet break-up at the higher flow rates.