Horizontal pipeline transportation of coarse particles: experimental investigation on flow patterns and velocity distribution

Efficient dredged material transport remains a key challenge in dredging engineering. To address this, this study built a dedicated experimental platform to explore the movement characteristics and resistance properties of coarse particles in horizontal pipeline transport. It tested different particle diameters, solid concentrations, and flow rates to systematically analyze the transport mechanism, and defined three particle bed types corresponding to different motion states of coarse particles. The results show that the three flow patterns have an overall logarithmic velocity distribution, with the velocity of coarse particles in the upper and lower pipe halves gradually decreasing as the distance from the centerline increases; particles differ significantly in water flow followability, among which 0.9 mm particles tend to promote flow pattern transition. Additionally, higher solid concentrations or larger particles expand the static sedimentation layer in the pipeline and delay flow pattern transition, so the concentration of dredged materials should be controlled at a moderate level in engineering practice to ensure transport performance.