| Abstract
| - In seeking validation of Dissipative Particle Dynamics (DPD) for the mesoscopic modeling of multiphasefluid−fluid systems in external fields, simulations of a pendant drop and a drop in simple shear flow havebeen performed. The shape profile of the simulated pendant drop was found to be in perfect agreementwith that computed by solving the Laplace equation. At increased values of the gravitational force (g), thedrop underwent considerable elongation, developing a “neck” between the solid support and its bulk part.Further increases in g resulted in thinning of the neck, which ruptured as g exceeded a certain value,leading to the detachment of the drop. This picture of the detachment process is consistent with theexperimental observations published in the literature. Also, the simulations reproduced the drop volumeexperiment quantitatively. For the drop in shear flow, the degree of deformation was found to be a linearfunction of the capillary number (Ca) in the region Ca ≤ 0.11, in good agreement with Taylor's theory;this is despite the fact that the hydrodynamic regime in the simulations (Re ∼ 1−10) is quite differentfrom that assumed in the theory (Re ≪ 1). At increased shear rates the results showed positive departurefrom linearity, in agreement with theory and experiment. Further increases in Ca resulted in the dropassuming a dumbbell like shape, the middle part of the “dumbbell” gradually stretching to form a thinneck. The rupture of the neck was occasioned by the instabilities manifested in the form of stochasticoscillations which magnified as the critical point was reached. The time evolution of the shape of the dropas it underwent the breakup process in our simulations bears remarkable similarity to the experimentalobservations of Torza et al. The critical value of the capillary number obtained in the simulations is inreasonable agreement with the experimental figure.
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