Rheometric flows of concentrated suspensions of solid particles

Publications on experimental and theoretical studies of the rheological properties of concentrated suspensions of solid particles have been analyzed. According to the currently accepted ideas, the rheology of suspensions is considered as a result of contact interaction of their constituent particles caused by the action of external forces, the formation and destruction of various types of conglomerate structures. A new rheological model of a highly concentrated suspension of solid particles in a Newtonian fluid is proposed, which describes both a continuous and discontinuous increase in the effective viscosity with a uniform increase in shear stresses. Accurate analytical formulas are obtained for the velocity profiles of suspensions in rotational viscometers “cone-plane” and “cylinder-cylinder”, as well as in a slit viscometer. The proposed model is modified to take into account the non-Newtonian properties of a dispersion medium, which exhibits pseudoplastic properties at low strain rates, and dilatant properties at large strain rates. The effective viscosity of such a suspension is presented as the sum of the contributions from the dispersion medium and the solid particles of the dispersed phase. To describe the rheology of the dispersion phase, the Ellis model was used. The velocity profiles in a pressure driven flat channel are obtained numerically by the finite element method. It is shown that, depending on the parameters of the model, the velocity profiles in a flat channel can take various complex forms.