Assessment on motion state changes and critical condition of coarse particles in pipeline hydraulic transport

The hydraulic transport in pipelines is one of the efficient transportation methods.The coarse particles have been widely used in the pipeline hydraulic transport in many practical engineering projects.However,since the coarse particle could easily settle in the pipeline,its movement is different from fine particles,and previously,very few studies have been reported in this field.In this study,the motion states and critical conditions of coarse particle movement in the horizontal pipeline are investigated experimentally under conditions of different particle sizes,volume concentrations and transport velocities.The results show that:(1) the ways that the coarse particles move in the horizontal pipeline involve suspended movement,rolling movement and sliding movement,and the sliding movement is the dominant motion state;(2) the motion states of coarse particles in the horizontal pipeline are correlated with the factors including particle size,volume concentration,pipe inside diameter and particle density.In this study,a critical condition formula is also proposed and validated by the experimental data.It is anticipated that the finding and the approach developed through this study can provide a technical reference for the hydraulic transport design of coarse particles in the pipeline.