Experimental study of hydraulic transport of large particles in horizontal pipes

This article presents an experimental study of the hydraulic transport of very large solid particles (above 5 mm) in an horizontal pipe. Two specific masses are used for the solids. The solids are spheres that are large with respect to the diameter of the pipe (5%, 10% and 15%) or real stones of arbitrary shapes but constant specific mass and a size distribution similar to the tested spherical beads. Finally, mixtures of size and/or specific mass are studied. The regimes are characterized with differential pressure measurements and visualizations. The results are compared to empirical models based on dimensionless numbers, together with 1D models that are based on mass and momentum balance. A model for the transport of large particles in vertical pipes is also proposed and tested on data available in the Literature, in order to compare the trends that are observed in the present experiments in a horizontal pipe to the trends predicted for a vertical pipe. The results show that the grain size and specific mass have a strong effect on the transition point between regimes with a stationary bed and dispersed flows. The pressure drops are moreover smaller for large particles in the horizontal part contrary to what occurs for vertical pipes, and to the predictions of the empirical correlations.