Applicability of the Dilatancy Model to Suspensions in Shear-thinning Medium

Abstract

The Applicability of the dilatancy model (Ookawara and Ogawa, 2000), which is based on the assumption that momentum flux is increased by particle collision, to suspensions in shear-thinning medium was examined experimentally. Aqueous solutions of 0.04, 0.06, 0.08 and 0.10 wt% polyacrylamide were prepared as suspending media. It was confirmed that these media showed shear-thinning properties and could be expressed by a power-law model in the shear rate range of 100–1,000 s^{− 1}. The indices of the model were 0.804, 0.759, 0.730, and 0.697, respectively. Suspensions of 10, 20 and 30 vol% polymethylmethacrylate particles, whose average diameter is 7 µm and density is 1,190 kg/m³, were prepared in these media. It was shown that the flow curves of these suspensions approached Newtonian with the increase of particle concentration and power-law model could not be applied. Therefore, the simultaneous application of classical suspension viscosity equation and the dilatancy model to these suspensions was examined. It was shown that a polynomial of degree 2 of the volume fraction and the dilatancy model could predict the flow curves of suspensions from the flow curves of media and particle concentrations.