Rupture and deformation of core-shell droplets under the action of rotating curved surfaces

This study employs numerical simulations to investigate the rupture and restructuring of core-shell droplets under the influence of rotating curved surfaces. The simulations are based on a multiphase lattice Boltzmann method coupled with the immersed boundary method. The effects of inter-surface distance, surface diameter, and contact angle under both tangent and separated conditions are systematically analyzed. The influence of inter-surface distance on the droplet aspect ratio, rupture time of droplet shell, and volume of daughter droplet follows a regular, positive correlation. In contrast, the effect of surface diameter on these parameters is more complex and coupled with the inter-surface distance. Under tangent conditions, the contact angle plays a significant role: when it is either too large or too small, surface tension can overcome rotational forces and dominate droplet migration. Typically, the deformation yields a sandwich-structured liquid film (tangent case) or droplet (separated case). However, results show that a sufficiently small contact angle (tangent case) or sufficiently small inter-surface distance and surface diameter (separated case) can transform the core-shell droplet into a two-layer liquid film or a Janus droplet, respectively.