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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)]. [ABSTRACT FROM AUTHOR]

Boundary-integral calculations are used to investigate the evolution of the shape of an initially nonspherical drop that translates at zero Reynolds through a quiescent, unbounded fluid. For finite capillary numbers, it is shown that the drop reverts to a sphere, provided the initial deformation is not too large. However, drops that are initially deformed to a greater extent are shown to deform continuously, forming an elongated shape with a tail when initially prolate, and a flattened shape with a cavity at the rear when initially oblate. The critical degree of deformation decreases as the capillary number increases and appears to be consistent with the results of Kojima et al. [Phys. Fluids 27, 19 (1984) ], who showed that the spherical drop is unstable to infinitesimal disturbances in the limit Ca = ∞. [ABSTRACT FROM AUTHOR]