A multi-core compound droplet passing through a diffuser channel

This study’s aim is to improve the understanding of the dynamical behavior of a multi-core compound droplet traveling in an axisymmetric channel consisting of a diffuser element. The compound droplet typically consisting of two inner droplets distributed one after another is initially located at a certain distance from the entrance of the channel. A front-tracking method is used to handle the movement and deformation of the droplet. The numerical simulation results show that the compound droplet is stretched in the channel, and it takes a certain time, “the transit time”, to pass through the diffuser. The compound droplet has the largest deformation in the diffuser region and tends to return to its nearly original shape after leaving the diffuser. The deformation and transit time of the compound droplet are affected by some typical parameters, such as the capillary number and the diffuser angle. For small capillary numbers, the leading inner droplet takes a shorter transit time than the rear one does. The transit time also increases with an increase in the diffuser angle and the number of inner droplets enclosed in the compound droplet.