Revisit of the Wall Effect on the Settling of Cylindrical Particles in the Inertial Regime

Abstract

The wall effect on the settling of cylindrical particles in the inertial regime is revisited. This study covers particle Reynolds number from 600 to 16 100 and particle-length-to-diameter ratios (l/d) from 4 to 21. The wall factor (Ut/Ut,∞) is found to decrease initially as the particle-to-column diameter ratio (d/D) increases. When the wall effect becomes significant, Ut/Ut,∞ starts to increase with an increase in d/D due to a change of the particle orientation during settling. After Ut/Ut,∞ reaches a maximum, it decreases to 0 when d/D increases to 1. A semiempirical model is developed to predict the wall effect of settling of cylindrical particles over the whole range of d/D. The model shows good prediction to the experimental results and matches the wall factor models developed for spherical particles when l/d approaches 1.