5 - Non-Newtonian slurries

Abstract

A Newtonian fluid is characterized by a linear relationship between the local shearing stress and the rate of strain within the moving fluid. Non-Newtonian fluids exhibit various types of nonlinearity. There are four types of non-Newtonian behaviors: Bingham plastic, Pseudoplastic, Newtonian, and Dilatant. These behaviors show how the rate of strain varies with the sheer stress that is applied to the fluid. The relationship between the local rate of deformation of the fluid and the shearing stress that is imposed differs from that which characterizes Newtonian fluids. This relationship is used to classify the flow behavious of various non-Newtonian fluids. The relationship between sheer stress and rate of strain of fluids can be measured in the laboratory and careful measurements can establish the rheological characteristics of any particular fluid. Dense slurries made from fine particles often behave as Bingham plastic at least approximately, and this is a useful model for these fluids. The Bingham plastic is an idealized model that can be used in theoretical calculations, but no real fluids ever behave exactly as a Bingham plastic.