Coalescence of drops in the Hele-Shaw geometry

Coalescence of drops is an interfacial fluid dynamics phenomenon commonly occurring in engineering devices as well as in nature. The physics of such coalescence has been studied mainly for three-dimensional (spherical drops) and semi-infinite two-dimensional (hemispherical drops) geometries. In contrast, the coalescence of drops in the pseudo two-dimensional geometries has been less documented. To investigate the coalescence of two drops of the same liquid in the Hele-Shaw geometry, we observed with the high-speed videography the neck growth of the two coalescing drops squeezed between two parallel hydrophobic surfaces. We also studied the effects of differences in liquid properties on the scaling behavior of coalescence.