Effect of the position of perpendicular pier groups in a sharp bend on flow and scour patterns: numerical simulation

Numerous bridges are destroyed worldwide every year mostly due to the role of hydraulic factors including scour being ignored when they are designed. Therefore, examination of the scour phenomenon around bridge piers in rivers and identification of the parameters affecting them gain a great level of significance. Particularly, if the bridge piers are installed at river bends, the complicated nature of the flow in bends adds to complications already existent in analysis of flow and scour patterns around such structures, which indicates the need for further study. Hence, the present study has utilized SSIIM numerical model to analyze the three-dimensional flow and scour patterns around perpendicular pier groups (two series of triad parallel piers) at different positions of a bended channel (at the 60-, 90-, and 120-degree angles). The simulated bended channel is a 1-m-wide channel with a central angle of 180 degrees and a relative curvature radius of 2. These data are first compared and confirmed with data collected by acoustic Doppler velocimetry under similar conditions for validation of the numerical data. The results obtained from this model indicated that changing the position of the bridge piers in the channel does not have a significant effect on the maximum scour value; however, the amount of the maximum sedimentation increases by 12% after relocating the piers from the 60- to the 90-degree angle, whereas relocating them from the 90- to the 120-degree position leads to a 42% reduction in the maximum sedimentation.