Solid-bowl batch centrifuges are used to thicken particulate and flocculated suspensions in many varied applications. The volume fraction dependent material parameters of compressive yield stress and hindered settling function are used to describe the solid/liquid separation of a two-phase system caused by centrifugal acceleration. The solution of the transient conservation of momentum and mass equations in radial coordinates gives the volume fraction distribution as a function of time for the two cases of the initial suspension networked or un-networked. Analytical solutions are given for the equilibrium distribution and the small-scale time dependence. The governing equations for the transient behaviors are solved using a 4(th)-5(th) order Runge-Kutta adaptive step-size numerical method. The results show three zones of behavior: a consolidating bed, a sedimentation zone, and a clear-liquor zone. The volume fraction within the sedimentation zone is constant for the initially networked case, and constant with radius but diminishing with time for the initially un-networked case. (c) 2005 American Institute of Chemical Engineers