
pmid: 12804217
Applications of the newly developed hybrid of the boundary integral and economical multipole techniques to large-scale dynamical simulations of concentrated emulsion flows of deformable drops are considered. For N = O(10(2)-10(3)) drops in a periodic cell with O(10(3)) boundary elements per drop, the method has two to three orders of magnitude gain over a standard boundary-integral method at each time-step, thus making long-time large-scale dynamical simulations feasible. In the steady shear flow, large systems N >/= O(10(2)) are imperative for convergence at high drop volume fractions c >/= 0.5. At high concentrations, most of the shear thinning occurs for nearly non-deformed drops; at c approximately 0.55 and small capillary numbers, phase transition is observed in dynamical simulations. In sedimentation of deformable drops from a homogeneous initial state, even larger N >/= O(10(3)) are required to accurately describe the Koch-Shaqfeh type of instability in a wide time range with N up to 1200 and ensemble averaging over the initial conditions. The dynamics of the average sedimentation rate is studied versus concentration c for matching viscosities lambda = 1; for a Bond number of 1.75, systems with c approximately 0.25 are found to be most unstable. Additionally, a low drop-to-medium-viscosity ratio system, lambda = 0.1, is more unstable than those with lambda = 0.25 and lambda = 1. In the third application, buoyancy- or gravity-driven motion of a large bubble/drop through a concentrated emulsion of neutrally buoyant drops is studied by simulations. For a size ratio of two, convergent (box-size independent) results for the bubble/drop settling velocity are obtained in simulations with N
Viscosity, boundary integral, multipole, emulsion, Stokes flow, deformable drop, Models, Theoretical, Elasticity, Fractionation, Field Flow, Motion, Suspensions, Boundary element methods applied to problems in fluid mechanics, Pressure, Computer Simulation, Emulsions, Stress, Mechanical, Rheology, Shear Strength, Simulation, Algorithms
Viscosity, boundary integral, multipole, emulsion, Stokes flow, deformable drop, Models, Theoretical, Elasticity, Fractionation, Field Flow, Motion, Suspensions, Boundary element methods applied to problems in fluid mechanics, Pressure, Computer Simulation, Emulsions, Stress, Mechanical, Rheology, Shear Strength, Simulation, Algorithms
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