关键词: 微流体学, 两相流, 计算流体力学, 微液滴, 流型

Abstract: Micro-droplet formation in the crossing micro-channel was numerically simulated by the 3D VOF model. Three flow regimes to generate droplet with monodispersity (squeezing, dripping and jetting) and other regimes (turbulent jetting, nodular flow, tubular flow, slip flow) were obtained. The simulation results agreed well with experiment observations, which validated the numerical model. The flow regimes were mainly affected by flow rate, surface tension and viscosity of two phases. With increasing flow rate of the continuous phase, droplet size would decrease and generation frequency would increase, whereas the effect of flow rate of the disperse phase was the opposite. Surface tension and viscosity of the continuous phase played a leading role under the conditions of high and low Ca number of the continuous phase, respectively. When Ca number was low, droplet size decreased in the squeezing and dripping regimes and increased in the jetting regime with decreasing surface tension, while generation frequency shows the reverse changing tendency compared with droplet size. When Ca number of the continuous phase was high, however, droplet size decreased with increasing the viscosity of the continuous phase, while generation frequency changed inversely. In addition, contact angel had little effect on the squeezing regime, but droplet could not be generated in the dripping and jetting regimes when contact angel decreased.

Key words: microfluidics, two-phase flow, CFD, micro-droplet, flow regime