Upper and lower bounds on the drag coefficient of a sphere in an Ellis model fluid

Abstract Hill's extremum principles are not directly applicable to an Ellis model fluid. A method of adapting Hill's principles to the Ellis model was developed and used to calculate upper and lower bounds on the drag coefficient for a sphere moving slowly through such a fluid. Available experimental data were compared with the average of the upper and lower bounds. Agreement was poor with Slattery's data and good with Turian's data. Some reasons to suspect Slattery's data have been pointed out.