Coalescence of viscoelastic sessile drops

Coalescence and breakup are classic problems in fluid physics that often involve self-similarity and singularity formation. Although the coalescence of sessile drops is inherently three dimensional, it has only been studied so far in two dimensions. Here, we experimentally and theoretically study the dynamic evolution of the three-dimensional shape of the interface during the coalescence of sessile drops. First, we will briefly summarize our findings regarding the three-dimensional self-similarity of the coalescence of Newtonian drops (joint work with A. A. Pahlavan and N. Xue). Then, we will explore some of the influences of elasticity on the dynamics. For polymeric drops, we show that the dynamics of the width of the bridge that grows outward on the substrate differs from the Newtonian case. We further study the three-dimensional evolution of the interface and investigate how elasticity modifies the coalescence behavior.