Effects of internal asymmetry on interface curvatures and outer drags determining the oriented shift of the eccentric globules

TL;DR

This study reveals that the oriented shift and inverse movement of eccentric globules in extensional flow are primarily driven by asymmetric interfacial curvature, influenced by internal structure and flow conditions, rather than external drag forces.

Contribution

The paper uncovers the dominant role of asymmetric interfacial curvature in globule shift, highlighting the effects of internal droplet positioning and flow parameters on globule dynamics.

Findings

Globule shift is mainly driven by asymmetric interfacial curvature.

Inner droplet size and position affect interface curvature and globule deformation.

Flow features like capillary number influence the shift direction.

Abstract

The physical mechanism of the oriented shift and inverse of eccentric globules in a modest extensional flow are investigated in this paper. Through this work, a shift of the globule, which is driven mainly by the asymmetric interfacial curvature, not by the outer drag, is disclosed. The asymmetric layout of the daughter droplet leads to the asymmetric drags from the continuous phase and the asymmetric deformation of the globule with different interface curvatures. As the inner droplet has both enhancing and suppressing effect on the globule deformation, the interface curvatures will vary when changing the relative size and location of the inner droplet. This curvature difference results in the asymmetric pressure distribution and circulation inside the globule. Eventually, the interaction of the inner driving force (pressure differences) and the outer drags causes the oriented shift and inverse of the globule. The shift direction is affected not only by the structural asymmetry parameter (eccentricity), but also by some flow features such as the capillary number. The results obtained here might enlighten potential applications for the movement of soft globules driven by curvature differences.