The effect of the pipe angle and protective inclined apron on the scouring and sedimentation pattern around a semi-buried pipe in a 90° mild bend

In fluid transmission projects, buried and semi-buried pipes passing through river bends change the conventional scouring and sedimentation patterns. In this research, the influence of pipeline angle in relation to flow direction in a 90-degree mild bend, along with the use of a protective inclined apron were experimentally investigated. Experiments were carried out in three different Froude numbers, three different passages (normal, repeller and attracting) as well as in the most critical condition, with three different protective inclined apron lengths. The results showed that in a condition where the pipeline passage is normal to the flow direction, the scour hole after the pipe is deepest, and in the repeller position, the most scouring was observed under the pipe. Moreover, placing a protective inclined apron, where the ratio of the apron length to the pipe diameter (LˊD) equals 1, reduces the amount of scour under the pipe by 75%. Furthermore, in the case where the ratio of the apron length to the pipe diameter (LˊD) equals 3 and 5, scouring under the pipe doesn't occur. •Using a 3D scanner to scan scouring and sedimentation profiles.•Evaluating the amount of scouring in 3 different pipe placement condition.•Studying the difference between scouring in the presence and absence of the pipe.•Studying the positive effect of protective inclined apron on the rate of scouring.