Unsteady Motion of a Type-A Compound Multiphase Drop at Moderate Reynolds Numbers

The shape evolution of a type- A compound two-phase drop is studied by means of a finite-element numerical simulation at moderate Reynolds numbers. The motion of the compound drop in the gravitational field is considered in the following two cases: (i) the free motion of type- A compound drops in a viscous fluid; (ii) the rise of type- A compound drops toward a rigid horizontal wall in a viscous fluid. The influence of the hydrodynamic parameters on the evolution of the shape of the compound drop is studied without any restrictions on the magnitude of its deformation. Some hydrodynamic effects such as a "dimpling," the appearance and disappearance of a concavity in the rear of the compound drop, and a change of the thickness of the thin liquid layer between the interfaces of the compound drop and between it and the rigid wall are observed. Comparisons with the experimental and theoretical results available in the literature are carried out and good qualitative agreements are achieved.