Computational rheometry of yielding and viscoplastic flow in vane-and-cup rheometer fixtures

A planar two-dimensional computational analysis is presented to qualify traditional and fractal vane-in-cup geometries for accurate rheometry of simple viscoplastic fluids with without slip. Numerical simulations based on an adaptive augmented Lagrangian scheme are used study the flow field yield-stress within around vane tools N=3 24 arms a wide range Bingham numbers, B (i.e. ratio yield stress over characteristic viscous stress). This allows calculations velocity fields vanes various geometries, as well direct comparison experimental observations output torque measured by rheometer, revealing sources variation error. We describe impact structure fluid field, from few-arm cruciform (N?6) that significantly perturb away ideal azimuthal kinematics, many-arm (N?12) in which internal structural features successfully “cloaked” surface. results shearing almost-circular ring indistinguishable annular deformed slip-free rotating cylindrical bob leads more rheometric measurements material curve. Moreover, data previous literature, we show slip conditions surface do not or overall T, whereas smooth outer wall have significant data, even when using geometry. Finally, topography number, B, accuracy “simple” (inelastic) described either plastic Herschel–Bulkley constitutive model.