Study On Interfacial Dynamics For Aqueous Glycerol Solution/Ionic Liquid Two-phase Flow In Microchannels

Microfluid control is a kind of science and technology that can accurately control and manipulate micrometer fluid.The dynamic behavior of liquid-liquid two-phase system in micro channel is the basis of the research and application of microfluid control technology.It is widely used in the process of mixing,emulsification,reaction and mass transfer.Dynamics of water-high-viscosity ionic liquid?[BMIM][PF₆]?two-phase flow in a flow-focusing device were investigated.Four flow regimes are identified:dripping,jetting,irregular and“string of sausages”.The transition lines between adjacent flow regimes are obtained on the flow patterns map based on the capillary number of the continuous phase and the Weber number of the dispersed phase.Due to the interaction of squeezing force,viscous shear force and surface tension,the rupture of the dispersed thread could be divided into the squeezing and the pinch-off stages.The size and frequency of the droplet and sausage were predicted respectively by a power-law function with the flow rate ratio and the capillary number.Droplet breakup with permanent obstruction and tunnel in an asymmetric microfluidic T-junction was investigated experimentally.The effects of the flow rates of both phases and the viscosity of disperse phases on the dynamical of droplet breakup are studied.Before the tunnel between the droplet tip and the microchannel wall appears during the breakup process,the minimum neck width experiences the similar process for permanent obstructed droplet breakup and the partly obstructed droplet breakup in the T-junction.The drop is squeezed by the continuous phase and droplet length increased gradually.In the process of droplet breakup,a scaling law is proposed to describe the variation of the minimum width of the droplet neck with time for the squeezing stage:?1-w_m/w_c????/?_T?^?.The prediction formula is presented to describe the minimum width of the droplet neck decreases with time for the pinch-off stage:w_m/w_c???T-??/?_T?^??Interfacial dynamics of the core-annular flow for immiscible fluids in a flow-focusing device were experimentally investigated.The viscosity ratio of the core stream to the sheathing stream ranged between 0.14 to 5.22.Three flow regimes were identified:tubular flow,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 rates and the viscosity 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.A stable and regular“sausage”wave was formed in a large two-phase flow rate range without external force or surfactant through experiment.The formation mechanism of“sausage”wave in the cross focusing microchannel and regulation of the characteristic size of“sausage”wave were systematically studied.The influence of different operating conditions on the characteristic size of“sausage”wave was investigated.Moreover,the prediction formulas of the initial length of the sausage wave,the wavelength and amplitude of the stable sausage wave and the formation frequency were presented.