Suction Effects on Sediment Transport in Closed-Conduit Flows

Laboratory experiments were conducted to investigate the influence of suction on sediment transport in closed-conduit flows in this study. The results show that the bed load transport rate essentially remains unchanged for small values of suction rates before abruptly increasing beyond a certain threshold. Theoretical analyses of the forces acting on a spherical particle also are conducted and a conceptual model set up to analyze suction effects on particle mobility by considering the near-bed velocities. The model hypothesizes that (1) the bed particle experiences an additional downward vertical drag force induced by suction; and (2) increasing suction will lead to larger horizontal and vertical near-bed velocities, which enhances both the driving force and effective weight of the particle. To qualitatively examine how suction affects the near-bed flow behavior, physical modeling capability software was used to simulate the physical system and the results confirm that the near-bed velocities increase with suction.