Interfacial settling mode and tail dynamics of spherical-particle motion through immiscible fluids interfaces

Abstract

Particles motion through a fluid-fluid interface is of both academic and industrial interests, yet, underlying mechanisms have not been fully understood. In this work, a two-phase LBM-DEM coupling model is developed to systematically explore the behavior of a particle moving through an immiscible fluid-fluid interface under different physical conditions. After validations, the current model reproduces two typical interface deformation modes, film drainage mode and tailing mode, successfully. The numerical results reveal that Reynolds number (Re = RV/ν) is not the key parameter governing the interfacial settling mode, because a smaller Re from larger upper fluid viscosity (ν) is conducive to the occurrence of tailing mode, but a smaller Re from smaller particle radius (R) or smaller settling velocity (V) makes film drainage mode take place more easily. The regime map in Capillary number (Ca) and viscosity ratio (λ) diagram shows that there exists a critical Ca characterizing the transition from film drainage mode to tailing mode, which is nearly independent of the viscosity ratio (λ) yet increases with the reduced particle size (R). The tail dynamics analysis shows that a higher Ca results in a larger final tail length and a pinch-off position closer to the middle of tail.