A recent publication based on experiments at Curtin University, Western Australia, proposed a new fall-velocity prediction technique that is more convenient than the traditional graph of drag coefficient versus particle Reynolds number. The new formulation predicts fall velocities without the need for iteration. It applies to particles in both Newtonian and non-Newtonian fluids, and is especially useful for the non-Newtonian case. This work is outlined and extended in the present paper. Analysis of the Curtin data indicates that the prediction accuracy of the new method is good for cases where the rheogram shape factor a is less than 1.7 (a ranges from 1.0 for a Newtonian fluid to a maximum of 2.0), and the accuracy then falls off for higher values of a, which generally reflect highly non-Newtonian behaviour at low shear rates - conditions for which rheological measurements are notoriously difficult. It has been found that particles which remain stationary in a quiescent non-Newtonian fluid usually settle when the fluid is subjected to an externally-imposed shear rate (as happens in pipeline flow). The focus of the present work has been extended to this case, leading to a proposed method of generalising the fall-velocity calculations. The method is illustrated by a design-oriented example.
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