Interfacial dynamics of the core-annular flow for glycerol–water solution / ionic liquid ([BMIM][PF 6 ]) two-phase flow in a microfluidic flow-focusing junction
Résumé
Interfacial dynamics of the core-annular flow for immiscible fluids in a flow-focusing device were experimentally investigated by using a high-speed digital camera. The viscosity ratio of the core stream to the sheathing stream ranged between 0.14 to 5.22. A series of solutions of glycerol in deionized water with various viscosities (35.49 mPa·s–1311.15 mPa·s) were used as the core stream, and the ionic liquid ([BMIM][PF6]) (251.76 mPa·s) was used as the sheathing stream. Three flow regimes were identified: tubing, convex core-annular flow and concave core-annular flow. The boundaries between adjacent regimes on flow patterns map were located. The effects of the flow rate ratio and the viscosity ratio of both phases, and the capillary number of the core stream on the characterized size of the core-annular flow were studied. The expressions are proposed for the expanding length and the diameter of the core stream. The present results provided a solid basis for microfluidic mixing, micro fiber synthesis and the design of the microfluidic system