Influence of suction and collar on reducing local scouring in cylindrical pier

Bridges are among the most important structures in river engineering. One of the significant causes of the destruction of bridges is local scouring around the piers. In the present research, collar and suction system both employed the upstream of the pier against local scouring. In separate experiments, the collar models were examined in different dimensions and the suction system was considered at different depth levels. Then, the combined collar-suction model was tested. The results showed that the suction system at the bed level (Z/h = 0) with the suction rate of (Qs/Q = 1.7%) had 51% efficiency; the 3D-length, 2D-width collar yielded 59% efficiency; and the combined suction-collar model had 94% efficiency in reducing local scouring of the pier by decreasing down-flow velocity, as well as the Reynolds Shear Stresses (RSSs) and Turbulence Kinetic Energy (TKE).