Scale similarity of sediment concentration in pressurized pipelines under complex terrain conditions

Abstract

Sediment deposition in pressurized pipelines under complex terrain conditions poses a serious threat to the safe operation of engineering systems. This study employed a combination of physical model tests and numerical simulations to examine the influence of geometric scale on sediment concentration and deposition characteristics in the descending, horizontal, and ascending sections of the pipeline. The results indicate that the radial sediment concentration decreased by more than 84% in the range of 0 < y/D < 0.3 except for the 1:2 scale. In the descending section, the scale similarity on sediment concentration is primarily controlled by the slope angle, and the scale effect becomes less pronounced with gentler slopes. In the horizontal section, the sediment concentration near the pipe bottom is positively correlated with the geometric scale, and the scale effect is more significant in shorter horizontal sections because of the stronger disturbance induced by the elbow flow field. In the ascending section, the scale effect is jointly governed by the inverted siphon size and elevation difference. At the 1:5 scale, the most severe deposition occurs in the ascending section with a relatively small elevation difference. Both sediment discharge and sediment deposition decrease exponentially with increasing geometric scale.