Derivation of Batchelor-Green formula for random suspensions

Abstract

This paper is dedicated to the effective viscosity of suspensions without inertia, at low solid volume fraction $\phi$. The goal is to derive rigorously a $o(\phi^2)$ formula for the effective viscosity. In previous works, such formula was given for rigid spheres satisfying the strong separation assumption $ d_{min} \ge c \phi^{-\frac13} r$, where $d_{min}$ is the minimal distance between the spheres and $r$ their radius. It was then applied to both periodic and random configurations with separation, to yield explicit values for the $O(\phi^2)$ coefficient. We consider here complementary (and certainly more realistic) random configurations, satisfying soft assumptions of separation and long range decorrelation. We justify in this setting the famous Batchelor-Green formula. Our result applies for instance to hardcore Poisson point process with almost minimal hardcore assumption $d_{min} > (2+\epsilon) r$, $\epsilon > 0$.