Flow in a ring-sheared drop: Drop deformation

The ring-sheared drop is a containerless system where shear imparted by two contact rings, one rotating and the other stationary. In microgravity, aqueous drops can be studied in air at centimeter scale. Drops of this scale also experimentally on Earth, but effects gravity need to mitigated density matching liquid its surrounding fluid. use silicone oil surrounded an solution allows while retaining viscosity ratio aqueous-air microgravity. imposed drives meridional flow which leads pear-shaped drop. A perturbation analysis with capillary number as small parameter used account for mean deformation. theory time-averaged experiments agree, particularly smaller ring rotation rates smaller. On top deformation, there amplitude nonaxisymmetric slower consists wave azimuthal wavenumber m = 1, that is, synchronous ring. This traced back imperfections wetting between experiment. At larger rotations, detect further unsteadiness broad frequency peak about third rate. Nonlinear simulations outer flow, assuming nondeforming drop, find these unsteady similar peak.