Scaling laws for bubble coalescence in power-law fluids

As two spherical gas bubbles in a liquid slowly approach each other, the liquid film or sheet between them drains and ultimately ruptures, forming a circular hole that connects them. The high curvature near the edge of the liquid sheet drives flow radially outward, causing the film to retract and the radius of the hole to increase with time. Experimental and theoretical work in this area over 2014-17 has uncovered self-similarity and universal scaling regimes when two bubbles coalesce in a Newtonian fluid. Motivated by applications such as polymer and composites processing, food and drug manufacture, and aeration/deaeration systems where the liquids often exhibit deformation-rate thinning rheology, we extend the recent Newtonian studies to bubble coalescence in power-law fluids. In our work, we reveal the full landscape of self-similar scaling regimes in the aftermath of the singularity over the full parameter space governing the merging of two bubbles into one.