Pipeline transport of coarse particles by water and by fluids with yield stresses

Experiments have been conducted using 1.7 mm and 4 mm particles transported in a pipe 52 mm in diameter. The carrier fluids were water and clay slurri es with yield stresses. In several experiments the yield stresses were high enough to support the particles in non-now situations. A two layer model was found to be appropriate for interpreting the pressure gradients, with both Coulombic and kinematic friction playing important ro les. Kinematic friction appeared to confirm recent experimental results obt ained with relatively coarse particles in vertical flows.