Spin-up of a Convected Maxwell Fluid in a Rotational Rheometer Modified to Allow Axial Flow

The rheological properties of suspensions and settling fluid mixtures may be measured using a rotational rheometer which has been modified to allow recirculation of the fluid after agitation in an adjacent chamber. Simulation of the behaviour of non-Newtonian fluids widely used in industry helps to determine limitations to the reliable use of this instrument. Of special interest is the spin-up of fluid in the cup prior to taking measurements of shear stress and shear rate at the surface of the bob. In this paper, the helical flow of a convected Maxwell fluid in the region between infinitely long coaxial cylinders is described. An implicit finite difference scheme which is conservative with respect to the axial flow rate is used to predict the response of the fluid to a prescribed angular velocity of the inner cylinder. The relationship between the damped oscillations in the transverse and axial velocity components and fluid viscosity parameters is discussed.