A Thermodynamical Theory of Fluid Suspensions

Abstract

A development is given of a thermodynamical theory of fluid suspensions of deformable particles. Assuming particles are spherical when undeformed and become ellipsoidal when sheared, linear constitutive equations are extracted from the general theory and restrictions on the material coefficients which appear in these linear constitutive equations are deduced by thermodynamical considerations. Applying this linear theory to steady shear flow of solutions for which particle interactions are negligible, it is found, solely by use of the thermodynamical restrictions on material coefficients, that the theory qualitatively predicts observed behavior in steady shear flow of dilute solutions of random coiling macromolecules, such as solutions of polyisobutylene. In particular, the resulting expressions for apparent viscosity t21/K and normal stress difference t11 − t22 are exactly those known to characterize experimental results for K≤103sec−1. For low shear rates K, the predicted value for the second normal stre...