Numerical investigation of droplet emulsion in flow-focusing and T-junction microfluidic devices

• Main Authors: Chien-Po Liu, 劉建伯
• Other Authors: Jerry M. Chen
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/78164934107625800576

碩士 === 國立中興大學 === 機械工程學系所 === 99 === In this investigation, the three-dimensional finite volume method (FVM) along with the volume of fluid (VOF) model was employed to simulate droplet formation in flow-focusing and T-junction microfluidics. Oil was taken as the continuous phase fluid and glycerol solution as the dispersed fluid to form water-in-oil droplets. In addition, the species equation was solved for comparison of binary mixing within the droplets generated during the emulsion process for both the flow-focusing and T-junction microfluidics. The mechanism of droplet emulsion is analyzed in terms of variations of energy for the dispersed phase fluid. It is found that the emulsion process can generally be divided into four stages, namely growth, elongation, break-up and shrinkage, according to the variations of kinetic energy, surface energy and pressure work computed for an entire period of forming an individual droplet. Moreover, the images of droplet formation in different types, including squeezing, dripping and jetting, were discussed with the energy variations. It is also found that droplets formed in a T-junction device are larger in size than that in a flow-focusing device, especially in the jetting regime. The simulations for two fluids mixed within the droplets show that the mixing efficiency for those formed in the T-junction always exceeds in the flow-focusing. This is mainly due to the fact that a pair of symmetric vortices developed within the droplets of dispersed phase fluids in the flow-focusing device while only one in the T-junction device that largely helps the advection of the fluids to be mixed.