There was an error in data reduction, resulting in incorrect values for the normal stress differences N 1 and N 2 shown in Figs. 7-10, and the corrected figures are shown here. In particular, the algebraic sign of N 1 is changed, as are the relative magnitudes of N 1 and N 2 . The negative values of N 1 for these non-shear-thickening suspensions are larger in magnitude than those reported by other workers, but both N 1 and N 2 are in general agreement with the accelerated Stokesian Dynamics calculations of Sierou and Brady [1].FIG. 7. Normal stress differences N 1 and N 2 of monodisperse suspensions at volume fractions of 0.4 and 0.5 for both 10 and 52.6 µm particles as functions of (a) shear rate and (b) shear stress (Insets are the same data on a semilog scale).
SYNOPSISWe have measured the viscometric functions of mono-and bimodal non-colloidal suspensions of PMMA spheres in a density-matched aqueous Newtonian suspending fluid using parallelplate and cone-and-plate rheometry for particle volume fractions in the range 0.20 to 0.50.Cone-and-plate normal stress measurements employed the method of Marsh and Pearson, in which there is a finite gap between the cone tip and the plate. The monodisperse suspensionsshowed an unexpected particle size dependence of the viscometric functions, with the viscosity increasing with decreasing particle size. Normal stresses were very small in magnitude and difficult to measure at volume fractions below 0.30. At higher concentrations, N 2 was negative and much larger in magnitude than N 1 , for which the algebraic sign was positive over most of the shear rate range for the monodisperse suspensions but indeterminate and possibly negative for the bimodal suspensions. The normal stresses were insensitive to bidispersity when plotted as functions of the shear stress at each volume fraction.