Critical friction factors during pipe blockage dislodgement in slurry flow

The purpose of this paper is to report on a laboratory investigation to measure the resistance due to the shear stresses at the pipe wall generated by a slurry column at conditions on incipient pipe blockage. Experiments were conducted in a vertical test reach using a mixture of sand and water with a pipe to particle diameter of 50. The resulting average friction factors were computed by application of the equation of motion to the recorded history of the motion and were found to be significantly larger than those computed using accepted correlations for steady heterogeneous flow. Compared to the pure fluid the average friction factor at incipient blockage was found to be between 400 to 800 times greater