Settling of spherical particles in unbounded and confined surfactant-based shear thinning viscoelastic fluids: An experimental study

▸ Settling velocities of spheres in shear thinning viscoelastic fluids are measured. ▸ Drag reduction at lower Weissenberg numbers (We) is observed. ▸ This is followed by a transition to drag increase at higher We. ▸ Elasticity is observed to reduce the effect of confining parallel walls. ▸ New correlations to quantify settling velocities are presented.