FLOW OF POWER-LAW FLUIDS IN CONE-PLATE VISCOMETER

The flow of a power-law fluid in a cone-plate viscometer has been considered. The first order solutions for velocity and pressure have been obtained. Effects of secondary flow on velocity components, pressure, rate of deformation tensors and apparent viscosity have been studied. Both the primary and secondary flows are influenced by flow behavior index 'n'. In shear thinning fluids, the effects on both the primary and secondary flows are of similar nature, whereas in shear thickening fluids, they are of opposite nature. The net result is that for shear thinning fluids the effects of the primary and secondary flows are additive, whereas in shear thickening fluids they almost balance out each other and the resultant effect is insignificant. The other important observation is in Newtonian fluids the secondary flow makes a significant contribution at high value of Reynolds number, which depends on the radius, velocity, density, and viscosity. In power-law fluids, Reynolds number depends on an additional parameter 'n'. With this change, the effect of secondary flows can be important even at low shear rates. A critical value of 'n' is obtained at which flow is independent of shear rates. © 1990 Springer-Verlag.