THE VISCOSITY OF A MODERATELY DENSE, POLYDISPERSE SUSPENSION OF SPHERICAL-PARTICLES

A recently developed formalism for computing the low-frequency, Newton ian viscosity of moderately dense monodisperse suspensions is extended to include polydisperse suspensions. In the form presented here this general theory is applicable to spherical solute particles suspended i n a Newtonian solvent. Explicit formulas are obtained for the viscosit y virial coefficients associated with first and second order terms in powers of the solute volume fraction. It is proved that the second ord er term in the viscosity virial series for a polydisperse suspension o f solute particles is fully characterized by a single, dimensionless f unction b(2)(lambda), with 0 less than or equal to lambda less than or equal to 1. Numerical values are presented for the second order (Hugg ins) coefficient specific to hard-sphere particles with general stick- slip solute-solvent boundary conditions and for ''spherical surfactant particles'' as well. Calculations are included also for suspensions w ith log-normal particle-size distributions. (C) 1998 Elsevier Science B.V. All rights reserved.