Effective viscosity of a periodic suspension

Abstract : The effective viscosity of a suspension is defined to be the four-tensor which relates the average deviatoric stress to the average rate of strain. The effective viscosity of an array of spheres centered on the points of a periodic lattice in an incompressible Newtonian fluid is determined. The formulation involves the traction exerted on a single sphere by the fluid, and an integral equation for the traction is derived. For lattices with cubic symmetry the effective viscosity tensor involves just two parameters. These are computed numerically for simple, body-centered and face-centered cubic lattices of spheres with solute concentrations up to 90% of the close-packing concentration. Asymptotic results for high concentrations are obtained for arbitrary lattice geometries, and found to be in good agreement with the numerical results for cubic lattices. The low concentration asymptotic expansions of Zuzovsky also agree well with the numerical results. (Author)