Coalescence of viscous drops

The coalescence of two viscous drops that are spreading near one another is a phenomenon that is rich in physics. As the two drops meet, a liquid bridge forms along the axis connecting the centers of the two drops. The width of the bridge has been shown to exhibit a power law growth at early times and the height profile of the bridge along the symmetry axis has been shown to have a local self-similar profile. Here, we study experimentally and theoretically the coalescence of two viscous drops on a highly wetting substrate. We use interferometry to resolve the evolution of the height profile in space and time and further investigate its self-similarity.