Wall effects on terminal velocity of non-spherical particles in non-Newtonian polymer solutions

This paper elucidates the effect of confining boundaries on the free falling velocity of variously shaped rigid particles in quiescent non-Newtonian shearthinning polymer solutions. Cylinders, needles, cubes and prisms, thin square plates and circular discs of different sizes and made of different materials (1200-8000 kg/m(3)) were sedimented in polymer solutions in cylindrical tubes of different diameters (20-100 mm). The hindrance effect due to the walls is quantified in terms of a wall factor which is a function only of particle size and shape, and tube diameter in the streamline region (Re < similar to 6-7). Simple expressions are put forward which correlate the present, as well as the previous scant, results satisfactorily.