Experimental study of bed topography variations due to placement of a triad series of vertical piers at different positions in a 180° bend

In this study, scouring around piers perpendicular to flow (PPF) and piers toward the flow (PTF) under clear-water condition was examined by placing a set of triad cylindrical piers with a 5-cm diameter and a 15-cm center to center distance at the positions of 60, 90, and 120 degrees of the bend at a constant flow rate of 70 1 per second. Natural sand of uniform grain size and average diameter of 1 mm with a uniformity coefficient of 1.3 was used as bed material of the flume. According to the results of this study, the maximum scouring depth occurred in the PPF test situated at the position of 90 degrees of the bend. In such a position, the maximum depth of scouring hole was equal to 1.1 times the depth of the flow at the beginning of the bend. Also, where the piers were positioned in PTF and PPF modes in a 60 degrees angle, the maximum area of scouring hole was observed around piers and sediment piles at the downstream side of the piers. The maximum height of sedimentation occurred in the PPF test situated at the 90 degrees position of the bend. Such a stack was as high as 0.7 times the flow depth at the beginning of the bend and was observed at the 156 degrees position of the bend, at a 20% distance of the flume width from the inner bank. Further results as well as discussion and analysis are among other points presented in the article.