Influence of slug flow on hydraulic sand dune migration in horizontal pipelines

This paper presents an experimental study of three phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of slug flow. Sand dune pitch, height and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for slug flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with slug flows. The sand dune local velocity (inside the slug body) was measured to be three times higher than the averaged dune velocities.