Investigation On Hydrodynamic Behaviors Of Double Emulsion In Bend Minichannel

Emulsion microfludics is the technology of regulating the volume, morphology and productivity of fluid precisely, based on designing the multiphase flow in the net of microfludic chip. Therefore, the technology has significant potential in a wide range of applications, such as the preparation of micro-energy material, micro-chemical control and micro-bio-pharmaceutical process. In summary, investigation on hydrodynamic behaviors of double emulsions in different channels has the significant theoretical and engineering values.Emulsion flow through bifurcation, bend and convergent-divergent channels, causing the dynamical behaviors such as droplet deformation, breakup and coalescence, which have significant effect on operation of emulsion microfludics. Although there have been several attempts on the hydrodynamic behaviors of emulsion droplet in convergent-divergent channel, the hydrodynamic mechanism of emulsion droplet in bend minichannel is still not completely understood. In this context, a theoretical model and a visualization experiment are performed to study the hydrodynamic behaviors of double emulsion in bend minichannel.An unsteady theoretical model for double emulsion motion in bend minichannels is developed and numerically analyzed. In this model, the liquid-liquid interface is captured by a volume of fluid (VOF) method. The phenomena of deformation and breakup of double emulsion in bend minichannels are explored, and the velocity and pressure contours during transient process are presented. The effects of bending angle, capillary number, inner drop, surface tension and oil viscosity on emulsion motion are analyzed. The results indicate that the centrifugal force cause deformation during the double emulsions flow through a bend minichannel. Increases in the bending angle bring in the increment in the deformation rate. Capillary number and surface tension are important factors that affect the hydrodynamic behaviors of double emulsion in bend minichannels. With increasing capillary number, the deformation rate of the emulsion is enhanced while the decrement in the deformation rate with increasing surface tension in the same bend minichannel. the deformation of double emulsion is hindered by increasing inner droplet in bend minichannel. Furthermore, the deformation of double emulsion is restrained by increasing oil viscosity.What's more, a visualization experiment on hydrodynamic behaviors of double emulsion in bend minichannel is conducted to gain an insight into double emulsion flow pattern transition, taking into consideration of flow rate and bending angle. The results indicate that, bending angle affects the hydrodynamic behaviors of double emulsion in bend minichannels. increases in the bending angle lead to the increment in the deformation rate. The size of double emulsion relies on flow rates of each fluid phase. A larger flow rate of outer fluid brings in the increment of the shear force which make the emulsion droplet deform easily.