Investigation of the reduction of sediment deposition and river flow resistance around dimpled surface piers

To reduce sediment accumulation in urban rivers due to the influence of cylindrical bridge piers on river flow resistance, the hydraulic performances of cylindrical piers were investigated using the computational fluid dynamics software FLOW 3D and compared with experimental data. The method included scouring and sedimentation analysis of piers and showed high accuracy at predicting experimental data. A dimpled surface pier was used as the model, and a series of simulations were conducted to evaluate its hydraulic performance. The results showed that scouring extents of a dimpled surface pier are larger than those of a cylindrical pier under different working conditions. This difference helped reducing sludge sedimenta-tion at the bottom of the river in the former. The ratio of the maximum sedimentation height to the pier diameter (d(h)/D), ratio of the sedimentation area, and cross-sectional area of the dimpled surface pier (A(h)/A(D)) are all smaller than those of a cylindrical pier at different flow velocities, indicating that dimpled surface piers have a lower silting probability. Compared with cylindrical piers, dimpled surface piers offer less interference to turbulent flow and generate a small-scale spiral flow; a lower lateral velocity is also obtained behind the dimpled surface pier, which leads to lower flow resistances and lower energy dissipation, which helps scour.