A Low-Cost Experiment on Newtonian and Non-Newtonian Fluids

An experiment to study the flow of Newtonian and non-Newtonian fluids is proposed. The method is based on measurement of the drag force on a sphere immersed in a moving fluid. The sphere–fluid relative velocity can be changed to obtain the dependence of the shear stress on velocity. This dependence shows the differences in flow of Newtonian and non-Newtonian fluids: decreasing viscosities with increasing velocities are obtained for shear-thinning fluids, while constant values of viscosity with velocity are obtained for Newtonian fluids. Although there is practical interest in the flow of non-Newtonian fluids, the high cost of commercial rotational viscometers used to determine the non-Newtonian behaviour makes them inconvenient for use as dedicated instruments in undergraduates' laboratories. The purpose of this experiment is to show Newtonian and shear-thinning flow to undergraduates using common components of a laboratory.