Numerical simulation of slug formation in micro-channels

We study the mixing of two immiscible fluids through a 90$^{\circ}$ junction of two micro-channels. The flow is simulated using both a particle-based method, dissipative particle dynamics (DPD), and a continuum Navier-Stokes approach with conservative level-set method. In both cases, immersed boundary methods simulate the walls. The Reynolds number is of the order of unity and the Weber number is varied for the purpose of the study. The measurement of the volume fraction of each fluid downstream of the junction exhibits a strongly periodic behavior. Under adequate conditions, micro-slugs that filled almost the entire width of the channel are formed. The simulation are compared with existing experimental data using water and octanol or aqueous glycerol. The flexibility of both codes is used to test optimization algorithms aiming at the control of the micro-slugs size and frequency. Preliminary results of this optimization study will be presented.