Analyses and simulations of a lab-scale device for determining floc strength are presented together with simulations of two different hermetic disc-stack centrifuge inlets. Two methods for determining the turbulent shear stresses on flocs in hermetic centrifuge inlets are described. A model for the average shear rate in a hermetic centrifuge inlet is proposed. A correlation for estimating the floc size of the centrifuge feed after passing the high-shear zone of the inlet is derived.