(160e) Coupled Level Set Volume of Fluid (CLSVOF) Study on Droplet Formation and Breakup Mechanism in a Flow-Focusing Device

Droplet based microfluidics have many potential applications in emulsions, drug delivery, material synthesis, and lab-on-a-chip. Demand for near monodisperse emulsion technologies has increased in recent years due to new advances in the production of microcapsules. Typically, droplets can be formed using T-junction or flow-focusing devices. Interestingly, in the open literature, most of the works reported based Volume-Of-Fluid (VOF) and Level set method (LS) interface capturing technique. To overcome the deficiencies of the LS method and the VOF method, in this study, Coupled level set volume of fluid (CLSVOF) method is used to track the interface between the two-phases. This approach enforces the mass conservation like VOF method. Surface tension force and the physical properties of the fluid are calculated in a similar method to the LS method. A three-dimensional illustration of the geometry of the flow-focusing device is considered with the square sections 600×600 μm is considered. The dispersed phase (oil) and the continuous phase (water) are introduced from the main channel and two side channels, respectively. At first, CFD model is validated with literature data and droplet length comparison showed good in agreement with. Developed model is thereafter extend to various parametric studies on effect of flow rate ratio, viscosity ratio and interfacial tension. The breakup process of the dispersed thread for high-viscosity aqueous phase studied in a flow-focusing device. Velocity field evolution during the droplet formation process is analyzed to understand the underlying physics of droplet breakup. The result shows that with increase in continuous phase flow rate, droplet length and volume decreases. At higher water flow rate, flow regime changes dripping to squeezing regime. In addition, the effects of Capillary number (Ca) on droplet length is investigated and it is found that interfacial forces significantly influence droplet length and formation mechanism. This work can help to understand the fundamental mechanism of droplet formation in flow-focusing microchannel. Furthermore, this work also emphasizes the importance of the fluid flow and the viscosity of the continuous phase to the breakup dynamics and the profile shape of the liquid–liquid interface, which is mostly neglected in previous studies.