A Study of the Sedimentation of a Sphere Near a Vertical Wall Using Three-Dimensional PIV

The sedimentation of a sphere through a fluid is a standard testbed problem in non-Newtonian fluid mechanics. The experimentally determined velocity fields may be compared with numerical predictions obtained using finite element simulations. In this work, the influence of an adjacent wall, in addition to elastic and shear thinning effects, on the velocity field in the fluid surrounding the sphere is studied. Three different test fluids are employed: a Newtonian reference fluid, a constant shear viscosity (elastic) Boger fluid, and a shear thinning elastic fluid. All three fluids have similar zero shear viscosities. For all experiments, the terminal velocity is achieved before measurements begin. Significant differences in both the location and magnitude of the recirculation zones are observed for the different test fluids. In addition, the shape of the wake is qualitatively different for the various fluids.