Experimental and numerical comparison of flow and scour patterns around a single and triple bridge piers located at a 180-degree sharp bend

Placement of bridge piers along rivers creates a complex 3D flow pattern which disrupts normal river flow and the resulted turbulence erodes alluvial sediments around the pier. In this research, SSIIM model has been used to simulate flow and scour patterns when no pier, one pier, and triple piers are placed at a 180 degrees bend and the results are compared with those of experiments. The piers are vertical. The simulated channel was 1 m wide with a U-turn having the relative curvature radius of 2 carrying a volumetric flow of 70 l/s the flow depth at the beginning of the bend is 18 cm. Results showed that SSIIM is well capable of simulating bed form changes and flow patterns such that at the bend with triple piers error in maximum scour and sedimentation was only 4%, in maximum transverse velocity 12%, in maximum longitudinal velocity 13%, and in maximum vertical velocity 19%. In general, SSIIM model satisfactorily simulates the location and value of local scour arising from single and series piers in numerical simulation of the flow and scour. In flow pattern simulation, the errors and differences are greater under moving bed conditions than a rigid bed.