(106a) An Experimental Investigation of Settling Velocity of Spherical Particles in Newtonian Fluid Using Particle Image Shadowgraphy Technique

The particle settling velocity is a fundamental requirement and key variable for modeling sedimentation processes and simulating particle transportations, especially when suspension is a main process. An experimental study has been conducted to measure the settling velocities of spherical particles with variable size and density in Newtonian fluids of variable viscosity and density.

The experimental technique (laser based image processing) is unique in its kind and it is very efficient in measuring the size, shape, and settling velocity of the particles, simultaneously.  The detailed experimental technique has been explained in this study. Experiments are conducted using five different types of spheres with five different type of Newtonian fluid. Different concentrations of glycerol-water mixture have been used as a fluid medium in the experiments. Rheology measurements have been conducted using cannon-Fenske viscometers.

Different models like Stokes (1951), Rubey (1933), Sha (1954), Concharov (1962), Gibbs et al (1971), Acharya (1976), Zanke (1977), Hallermeier (1981), Dietrich (1962), Van Rijn (1989), Julien (1995), Darby (1996), Soulsby (1997), Cheng (1997), Ceylan (1999), and Helbar (2009) have been studied and their prediction ability are critically analyzed.   Based on the results from the particle image shadowgraphy experiments, a new dimensionless model for predicting settling velocity for a wider range of particle size and flow regime has been developed.

The new model predictions have been compared with the other experimental results from the literature and are found to be matching within range of error less than 7%. When compared with the other models present in the literature, the new model is unique by its simplicity in use and its efficiency in predicting the settling velocity of spherical particles.