Evolution of symmetrical microvortices in a generating microdroplet during neck breakage stage in an altered T-shaped microchannel

Vortices are a fascinating flow phenomenon and an important research topic in fluid mechanics. In this study, the evolution of symmetrical vortices within a generating droplet in an altered T-shaped microchannel was investigated using microparticle image velocimetry (micro-PIV) and high-speed imaging microscopy. Transient flow patterns within the microdroplet were visualized in the focal plane, revealing a high-speed jet flow and two counter-rotating symmetric vortex pairs. These findings suggest that the internal flow field of the microdroplet exhibits intricate three-dimensional structures. The vortical flow behaviors were quantitatively characterized in detail by calculating the vorticity, rotation, shear deformation, and tensile deformation. These results are crucial for comprehending the initial flow dynamics and mixing processes occurring within generating microdroplets.