Effects of fluid elasticity on the static and dynamic settling of a spherical particle

Abstract

The results of an experimental investigation of the settling velocity of spherical particles in viscoelastic fluids are presented. As well as being fundamentally interesting, this problem is also of relevance to the under- standing of particle transport by well-technology fluids used in the oil industry. It is shown that the settling velocity is reduced by elastic effects in the fluid (e.g., presence of normal stress differences and high elongational viscosity), and that this effect becomes significantly higher with increasing shear rates experienced by the falling sphere, i.e. the ratio of settling velocity to sphere diameter. Imposing an orthogonal shear-flow field on the settling particle causes a further dramatic reduction of the settling velocity in viscoelastic fluids.