Studying the Factors Affecting the Drag Coefficient of Free Settling in Non-Newtonian fluid

The aim of this research is to study the effect of rheological properties ,concentrations of non-Newtonian fluids, particle shape, size and the density difference between particle and fluid on drag coefficient (C) and settling velocity (VS), also this study show the effect drag coefficient (C)and Reynolds' number (Re) relationship and the effect of rheological properties on this relationship.P An experimental apparatus was designed and built, which consists of Perspex pipe of length of 160 cm. and inside diameter of 7.8 cm. to calculate the settling velocity, also electronic circuit was designed to calculate the falling time of particles through fluid.Two types of solid particles were used; glass spheres with diameters of (0.22, 0.33, 0.4, 0.6, 0.8, 1, 1.43, 2) cm. and crushed rocks as irregularly shaped particles with different diameters (0.984, 1.102, 1.152, 1.198, 1.241,1.388, 1.420, 1.563, 1.789, 1.823, 1.847, 2.121 ) cm and compared with each other. The concept of equivalent spherical diameter (Ds) was used calculate the diameters of irregularly shaped particles.The settling velocity was calculated for Non-Newtonian fluids which represented by Power-Law fluid. Two types polymers were used, Carboxy Methyl Cellulose with concentrations of (3.71, 5, 15, 17.5) g/l and polyacrylamide with concentrations of (2, 4, 6) g/l and compared with Newtonian fluid which represented by water.The results showed that the drag coefficient decreased with increasing
settling velocity and particle diameters and sizes; and increased as fluid become far from Newtonian behavior and concentrations and the density difference between particle and fluid. The results showed that the rheological properties of Non-Newtonian fluids have a great effect on the drag coefficient and Reynolds number relationship, especially in laminar-slip regime and decreases or vanishes at transition and turbulent-slip regimes.