Slow parallel motion of cylinders in non-Newtonian media: wall effects and drag coefficient

Abstract

The terminal velocity of numerous cylinders of Perspex and glass in a parallel orientation has been measured in a series of polymer solutions. The rheological behaviour of the test liquids could be approximated by a power law model. The significance of wall effects has been demonstrated by carrying out experiments in four fall tubes of different diameters. The experimental results embrace the following ranges of conditions: cylinder to fall tube diameter ratio, 0.0785-041; length to diameter ratio, 1.4-2; power law index, 0.48-0.62; and Reynolds number, 3.8 × 10^-4-1.27. The wall effect results are analysed and discussed in a manner analogous to those for spherical particles. The free fall velocity data are analysed using a drag coefficient-Reynolds number method. Appropriate predictive formulae have been developed.