Mohammad Vaghefi

Placement of bridge piers along rivers forms a complex 3D flow pattern that disrupts normal river flow and the resulting turbulence erodes alluvial sediments around the pier. This study employed Sediment Simulation In Intakes with Mult-block option (SSIIM) model to simulate flow and scour patterns when no pier, single pier, and triple piers were placed at a 180-degree bend, respectively, and the results were compared with those of previous experiments. The piers were vertical. The simulated channel was 1 m wide with a U-turn of a relative curvature radius of 2 that carried a volumetric flow rate of 70 l/s and the flow depth at the beginning of the bend was 18 cm. Results showed that SSIIM could effectively simulate the changes of bed form and flow patterns so that the error at the bend with triple piers would be only 4% in maximum scour and sedimentation, 12% in maximum transverse velocity, 13% in maximum longitudinal velocity, and 19% in maximum vertical velocity. In general, SSIIM model satisfactorily simulated the location and value of the local scour arising from both single and series piers in numerical simulation of the flow and scour. In the flow pattern simulation, the errors and differences are greater in the moving bed conditions than a rigid bed.