WALL EFFECTS ON FREE-SETTLING VELOCITY OF NONSPHERICAL PARTICLES IN VISCOUS MEDIA IN CYLINDRICAL-TUBES

This work sets out to investigate the effect of confining walls on the settling velocity of variously shaped rigid particles in stationary Newtonian liquids. Cubes, parallelepipeds, cylinders, needles, thin plates and circular discs of different sizes and made of different materials (1200-7800 kg/m(3)) have been sedimented in scores of liquids in cyclindrical tubes of different inside diameters (20-100 mm). The retardation effect due to the presence of bounding walls has been quantified in terms of a wall factor which is a function only of particle size and shape, and tube diameter in the low Reynolds number region ( < 7). Simple expressions are presented that not only correlate well the present results but also describe satisfactorily the scant literature data.