3-DIMENSIONAL IMMISCIBLE LATTICE-GAS - APPLICATION TO SHEARED PHASE-SEPARATION

A new lattice-gas cellular automaton model for simulating binary fluid s in three dimensions is introduced. It is particularly suitable for m odeling slow flows of mixtures with complicated interface geometries o r within complicated boundaries, such as in the interior of a porous r ock. Phase separation is triggered spontaneously in the model by stati stical fluctuations and phase domains are approximately isotropic. The measured surface tension is large compared to that in analogous two-d imensional models. The model is applied to a study of the time-depende nt effective viscosity of a phase-separating mixture in a simple shear flow. Results qualitatively match both experiment and theory: the vis cosity increases rapidly, then decays gradually to a steady-state valu e which is larger than the viscosity of the pure fluids. The effective viscosity increases with increasing concentration and decreases with increasing strain rate.