Laminar settling of glass beads in visco-plastic liquids

quiescent visco-plastic liquids of Herschel-Bulkley type. Experiments on laminar settling of glass
beads of different sizes were conducted in transparent Carbopol solutions of various rheological
properties in a sedimentation column. The terminal settling velocity of a solitude bead was
determined together with the rheological parameters of the Carbopol liquid. An evaluation of the
experimental results confirms the existence of the laminar regime for all tests and compares the
measured velocities with predictions by Wilson et al. method. Furthermore, an alternative method
is proposed for a prediction of the terminal settling velocity in the laminar regime which uses a
particle-based determination of the strain rate in the expression for the equivalent viscosity. A
comparison with our experimental results shows that the predictions using the proposed method
agree well with the experiments and the proposed method is in the laminar settling regime more
accurate than the Wilson et al. method.