The flow of sand/water slurries in horizontal pipes with internal spiral ribs — effect of rib height

The effect of secondary flows created by an internal spiral rib in an otherwise conventional smooth 2‐inch pipe on the transportability of “settling” suspensions of sand in water was investigated with emphasis on the effect of rib height. While the ribs were found to be a disadvantage at relatively high average mixture velocities because of increased pressure gradients, they were advantageous at low velocities. The deposit velocity and the pressure gradient at the deposit velocity in ribbed pipes of several pitch to diameter ratios and rib heights were correlated with respect to the corresponding smooth pipe values. These correlations are useful in pipeline design. The optimum rib geometry was estimated to be a pitch to diameter ratio of about 8 and a rib height in the range of 10–15% of the pipe diameter for the solid‐liquid mixtures investigated.