Numerical study of double emulsion droplet generation in a dual-coaxial microfluidic device using response surface methodology

This paper presents a parametric study using a three-phase axisymmetric numerical simulation on a dual co-axial microfluidic device for creating compound droplets. The Volume of Fluid-Continuum Surface Force model (VOFCSF) was developed to perform a parametric analysis of the double emulsion formation in a dual co-axial microfluidic device. The model was used to investigate the effects of phase velocities, viscosities, and interfacial tensions on the size and generation rate of the double emulsions, with the assistance of the Design of Experiments (DOE) and Response Surface Methodology (RSM). The DOE considerably decreased the number of simulations. A sensitive analysis revealed that the outer phase parameters have the most noteworthy influence on double emulsion characteristics. Dimensionless numbers, including Weber number of the inner phase (Wein), the capillary number of the middle phase (Camid), and the capillary number of the outer phase (Caout), were also implemented to examine the effects of essential forces on the double emulsion size. The simulation results verified that the size of both the inner and the outer droplets could be easily adapted within a broad range by adjusting non-dimensional parameters. The simulation results can be utilized to generate a broad range of liquidliquid encapsulated structures.