CONCENTRATION DISTRIBUTIONS OF SAND SLURRIES IN HORIZONTAL PIPE-FLOW

Concentration distributions for sand slurries flowing in pipes of diameter ranging between 50 and 500 mm have been measured. Particle diameters ranged between 0.18 and 2.4 mm. The concentration distributions have been used in a critical examination of the suspension mechanisms for flows without stationary deposits. Although the classical Schmidt-Rouse diffusion mechanism applies for slurries of fine particles, a pipe diameter dependence of the diffusion coefficient has been detected. This deviation could be due to a form of turbulence suppression by the density gradient in the slurry. For large particles, settling velocities and flow velocities were found to be of minor importance. Particle interaction effects appeared to be confined to the near-wall regions and were most important for the largest particles in the smallest pipe. A method for predicting concentration distributions in the absence of particle interaction effects is proposed.