A New Generalized Model for Predicting the Drag Coefficient and the Settling Velocity of Rigid Spheres in Viscoplastic Fluids

Abstract

Summary An experimental study was conducted to measure the settling velocity of spherical particles in viscoplastic fluids exhibiting inelastic and elastic behavior. Using a mechanistic model dependent on the balance of the forces acting on the settling particle and detailed statistical analyses of the experimental results, a generalized model for predicting the settling velocity of spherical particles in viscoplastic fluids was developed. A new modified shear Reynolds number (ReT*) was introduced, which physically quantifies the effects of non-Newtonian-fluid rheological properties on the settling velocity. The newly developed CD/Rep correlation and the modified shear Reynolds number were incorporated into the Wilson et al. (2003) model to develop a generalized model that can be used for predicting the particle-settling velocity in all types of viscoplastic fluids.