Modelling high concentration settling slurry flows

The well-known two-layer model for predicting friction losses for pipeline flows of settling slurries has been extended to solids concentrations above 35% by volume. This has been achieved by incorporating new experimental results to account for increases in friction which have been observed with "settling" slurries at high concentrations. The kinetic (fluid-like) friction appears to increase with solids concentration in a manner which suggests that particle-wall contact plays an important role. The experiments also suggest that the fraction of the total solids which contributes Coulombic (velocity insensitive) friction also increases to some extent at high concentrations. This effect is expressed in a tentative correlation which employs a slurry Reynolds number. In addition, new experimental measurements of delivered and in-situ concentrations have been used to test predictions made with the previous version of the model. The measurements show that the interfacial friction factor proposed recently by Wilson and coworkers is preferable for slurries of coarse particles.