Generation of Newtonian droplets in Newtonian and non-Newtonian carrier flows in micro T-junctions under opposed-flow configuration

In this paper the generation of Newtonian microdroplets in both Newtonian and non-Newtonian carrier fluids through a commercial micro T-junction under an opposed-flow configuration is analyzed experimentally. Pure deionized water and 0.2 wt% aqueous Xanthan gum solution in presence or absence of surfactant (Tween 20) have been considered as carrier fluids and the silicone oil is employed as the dispersed phase. The role of surfactant as a promoter of the generation of a droplet-based flow at the outlet of the T-junction is analyzed. Squeezing, dripping, jetting and parallel flow regimes have been generated by varying the flow rates of the dispersed and continuous phases at the inlets of the junction. A series of flow maps is presented in order to facilitate the design prediction of the droplet flow patterns generated at the outlet of the junction by varying the Capillary number and/or the inlet volumetric flow rates of Newtonian and non-Newtonian fluids. In the current paper, detailed information about the typical values of the droplet breakup distance from the center of the T- junction is demonstrated and the typical droplet length and polydispersity values are studied as a function of the inlet flow rate ratio and Capillary number.