Interfaces Coupling Deformation Mechanisms of Liquid-Liquid-Liquid Three-Phase Flow in a Confined Microchannel

Interfaces coupling deformation mechanisms of liquid-liquid-liquid three-phase flow in a confined microchannel are ascertained by both experimental investigation and numerical simulation. The deformation behaviors of inner and outer interfaces of compound droplets mainly depend on the flow rate of continuous phase (Q) and the diameter ratio of core droplet to shell droplet (D*). Compared with that of single droplets, the outer interface deformation degree of compound droplets is always limited at large Q and D* because of the hindering effect of inner interface. However, the hindering effect can be weakened by decreasing the D*, and thus the outer interface deformations for both single and compound droplets remain almost consistent. Additionally, the in-terfaces coupling deformation mechanisms are also clarified, and the results show that due to the existence of outer interface, the differential pressure force and shearing force acting on the inner interface decrease, resulting in a low deformation coefficient of core droplet. The influence of inner interface on outer interface deformation is only reflected by the disturbance to the flow field structures. To achieve precise control over the outer interface deformation, a prediction correlation for aspect ratio with several dimensionless numbers is established with good precision. The results in this study provide valuable guidance for practical applications of liquid--liquid-liquid three-phase flow microsystems.