On the flow of a stress power-law fluid in an orthogonal rheometer

The orthogonal rheometer, an instrument developed by Maxwell and Chartoff (1965) that has been used to measure the properties of non-Newtonian fluids, is essentially two parallel disks rotating about non-coincident axes with the same angular speed. By measuring the forces due to the flow of the fluid, and corroborating the constitutive relation with the same, one can determine the material moduli that characterize the fluid. In this paper, we discuss the flow of a novel constitutive relation that has been developed to describe the response of colloids. We find that pronounced boundary layers adjacent to the rotating plates can develop even at moderate Reynolds. These boundary layers are not necessarily restricted to inertial boundary layers. The flow patterns are also markedly different from those for the classical Navier–Stokes or power-law fluids.