3-D particle image velocimetry of the flow field around a sphere sedimenting near a wall Part 2. Effects of distance from the wall

Through the use of stereoscopic 3-D particle image velocimetry (3-D PIV), the flow field surrounding a sphere sedimenting at a distance of one, two and three ball diameters from the wall is measured. A Newtonian (constant shear viscosity, inelastic) fluid, a Boger (constant shear viscosity, elastic) fluid and a shear-thinning (variable shear viscosity, elastic) fluid are used to study the effects of shear-thinning and elasticity. There are significant differences in the flow fields that can be observed for the different types of fluids and the different distances from the wall from which the sphere is dropped. We find that the structure of the flow field and the motion perpendicular to the wall are dependent on the distance from the wall at which the sphere sediments. (c) 2005 Elsevier B.V. All rights reserved.