Study Of Inner Flow In The Rheological Behaviors Of Multiple Emulsion Globule

Droplet-based microfluidics have unique advantages and wide applications in the preparation of multifunctional multiple emulsions and microchip laboratories(Lab-onchip).When the multiple emulsions have been prepared,delivered or released in the microfluidic device(usually microchannels),the globules suspended in immiscible continuous phase are often confined by the geometry of the microchannels and fallen under the viscous shear stress.Double-emulsion globule will show several rheological behaviors including deformation,break-up and merging.The study of rheological behaviors of multiple emulsion globule in microchannel has some basic significance for future experiments.In this paper,the rheological behavior of the asymmetric double-emulsion globules under the steady extensional flow in cross microchannel and the change of the inner flow field are investigated respectively;Meanwhile,the rheological behavior of the double-emulsion globules under the inner uniform spin shear flow field in the infinite region and the microchannels are investigated by the simulation numerical method respectively.The numerical simulation method is based on two-dimensional spectral boundary integral methods.The numerical algorithms are compiled into the CVF language.The effect of capillary numbers and internal structures on the orientation of the asymmetric double-emulsion under steady extensional flow are investigated numerically.Meanwhile,we explore the pressure difference between the two ends of the droplet and the force of the extension flow to the droplet boundary.The above two parameters are directly corresponding to the pressure difference and total force.Finally,the directional flow field generated inside the double-emulsion globules is same with globule shifting direction.Driven by the directional flow field,the eccentric compound globules move off the stagnation point in the cross-channel.Most of previous studies were mainly about the influence of external flow field on droplet deformation and migration,or the influence of electric field driving streamline on globule rheology.This paper compares the similarity and difference of the deformation of the double-emulsion globules under the internal spin shear flow field under infinite region and microchannels.Two different modes of break-up are found,and the influence of the viscosity ratio,the capillary number and the solid surface of the microchannel on the deformation of the double-emulsion is also explored.In addition,the effect of the flow field on the droplet rheological behavior through the Fluent triangular dynamic mesh model,which is generated by the uniform linear motion of the solid particles inside the droplets,is investigated by the two cases with different viscosity ratios.Where the hinder boundary of the globule opposite to the direction of the inner solid particle is concave under the action of viscous force,and the greater the viscosity ratio,the greater the degree of sag.