Stable and reliable micro jets are important for many applications. Double flow focused micro jets are a novelty with an important advantage of significantly reduced sample consumption. Numerical simulations of double flow focused micro jets are a highly complex task. They represents a great computational challenge due to the multiphase nature of the problem, strong coupling between the gas and the two liquids and the sub-micron size cells needed. Simulations were performed with the open source computational fluid dynamics toolbox called OpenFOAM. Two multiphase solvers were used, one of which was modified in order to properly describe the interface between the focusing liquid and the gas. In this study two different incompressible physical models were considered and compared. A model with no mixing of the two fluids (multiphaseInterFoam solver) and a model where the diffusion of the two fluids is permitted (modified interMixingFoam solver). The results of simulations for the two different physical models using the same inlet parameters are presented. Additionally, a parametric analysis for the mixing case was performed to study the effects of different parameters on the jet formation. Particularly how the different diffusion values couple with the jet length, diameter and its stability. Results show a match in jet diameter and jet length for both models when the same set of parameters is used
