Near-contact motion of liquid drops in emulsions and foams

A computational and analytical study of the near-contact motion of liquid drops with tangentially mobile interfaces is presented. It is shown that flow in the continuous-phase thin-liquid film separating the drop interfaces is coupled to flow inside the drops, in contrast to previous analyses in the literature which have ignored this coupling under small deformation conditions. In this thesis, three fundamental problems pertaining to this coupling are solved: drop coalescence in a quiescent fluid, the effect of an ambient flow on drop coalescence, and the effect of near-contact motion on the rheology of concentrated emulsions and foams.;For the problem of drop coalescence in a quiescent fluid, the film-drainage dynamics are determined using a lubrication analysis and contrasted to previous work which assumed that tangentially mobile and immobile interfaces drain in qualitatively similar ways. The dynamics of drop coalescence in the presence of an external flow are also analyzed to determine the importance of an external flow field on the thin-film drainage dynamics.;The effect of drop near-contact motion on the linear-viscoelastic response of concentrated emulsions and foams at volume fractions above and below maximum packing for undeformed drops is determined by numerically solving Stokes' equations for the flow due to linear perturbations of the system from an equilibrium state. The rheology at volume fractions above and below maximum packing are compared and contrasted to results in the literature.