Particle Settling Velocity in Slurry Stirred Vessels

The aim of this work is to investigate the settling behavior of solid particles suspended in a liquid phase under fully turbulent conditions. To this purpose, the mean velocities of water and glass particles in a standard geometry stirred tank are simultaneously measured by a two-phase Particle Image Velocimetry technique. The deviation of the particle settling velocity from the terminal velocity value, which can be associated to the liquid free stream turbulence, is analyzed. A simplified approach to extract information from the collected PIV data on the different contributions to the force balance equation on a single particle is proposed. From the analysis of the results, the dominant contribution of the drag force over the other forces acting on the particles is found. The appropriateness of previous correlations for estimating the particle settling velocity and/or the particle drag coefficient in turbulent fluids, which are based on the ratio between the particle diameter and the Kolmogoroff length scale, is assessed.