An experimental investigation on the stability of viscous drops translating through a quiescent fluid

The evolution of the shape of an initially nonspherical drop translating at low Reynolds number through a quiescent fluid is investigated experimentally. It is found that the drop reverts to a spherical shape when the degree of initial deformation is small enough. However, drops that are highly deformed initially are shown to deform continuously. Specifically, a prolate drop breaks up into multiple droplets as it rises, while an oblate drop deforms into a double-emulsion drop as it translates. The experimental results agree well with results obtained earlier from numerical simulations [Phys. Fluids A 1, 1309 (1989)].