THE APPLICATION OF DYNAMIC CLUSTERING DATA TO THE SEDIMENTATION-RATESOF CONCENTRATED SUSPENSIONS

A modified Stokes equation is proposed for the settling of concentrate d suspensions of spherical particles in Newtonian fluids. The proposed hindered settling model was derived semi-analytically incorporating d ata obtained on dynamic particle clustering in concentrated suspension s by Graham and Bird. The approach differs from previous models which either neglected the influence of one particle on another or treated t hese interactions in an empirical manner with minimal physical or mech anistic basis for their design. The phenomenon of dynamic clustering w hich has recently been observed experimentally and shown to occur in f lowing suspensions and sedimentation provides the basis for this study . Cluster size distributions are estimated based on suspension propert ies and a summation of Stokes terms provides a settling velocity predi ction of concentrated systems. The validity of the model is supported by comparing calculated sedimentation rates with measured values for a number of data sets obtained from a variety of different authors.