Apparent viscosity of suspensions of rods using falling ball rheometry

Falling ball rheometry measurements of the apparent relative viscosity of suspensions of randomly oriented rodlike particles are reported for rods having a wide range of aspect ratios and concentrations. These data, combined with those from earlier studies [Milliken et al., J. Fluid Mech. 202, 217 (1989); Powell et al., J. Rheology 33, 1173 (1989)], provide a master curve describing the apparent viscosity in terms of a single parameter, nL3, where L is the length of the particle and n is the number density.