ANALYSIS OF THE DRAG REDUCING REGIME OF PULP SUSPENSION FLOW

Abstract

Under certain conditions of turbulent flow, values of friction loss for wood pulp fiber suspensions are lower than those for water at the same flow rate. This phenomenon of drag reduction is discussed with reference to pipe flow, and results from an investigation of flow resistance and velocity profiles of turbulent fiber suspensions are reviewed. Analytical expressions relating velocity profiles and flow resistance are derived and supported with experimental data. These relationships can be used to predict flow resistance in piping systems. Drag reduction also occurs when a rotating disk is immersed in a suspension of wood pulp fibers, and a method is proposed for predicting pipe friction loss and velocity profiles for fully developed turbulent flow in pipes from torque measurements obtained from a rotating disk. The method has been applied successfully over a limited range of conditions.