End effects in rotational viscometry I. No-slip shear-thinning samples in the Z40 DIN sensor

Neglect of end effects in Couette rotational viscometry introduces a 10–30% error in the estimate of shear stress at the spindle surface. Actual deviations depend on the shear-thinning level of a given sample. We tackle the end effect for the standard sensor Z40 DIN according to the ISO 3219 by solving the related 2D boundary-value problem for a class of shear-thinning viscosity functions. The pseudosimilarity method of treating the primary data leaves an error of about 0.5% in shear stresses. Further reduction in the errors needs a full numerical simulation for each point of the primary data based on a suitable wide-range representation of the viscosity function. To support a high accuracy of torque calibrations, the effect of inertia on torque for Newtonian liquids in standard sensor Z40 DIN at Re < 500 is calculated using the FLUENT 6.2 commercial software.