Flow-induced shape optimization of bridge piers using cfd analyses and adjoint method

The majority of damages occurring in the bridges constructed over rivers mainly attributed to hydraulic reasons. One primary hydraulic factor resulting to these damages is the clean water scour around the bridge piers. The bridge piers alter the flow pattern of the river, causing the transportation of natural materials in the riverbed and consequently compromising the structural integrity of the bridge piers. Specifically, the shape of the bridge pier is known to have a significant impact on the scouring phenomenon. This study focuses on the flow-induced shape optimization of a commonly used cylindrical bridge pier geometry using Computational Fluid Dynamics and adjoint shape optimization methods. The main objective is to reduce the shear stresses acting on the rigid riverbed while preserving the cross-sectional area and the projected area of the pier in the flow direction. Transient analyses are performed using Large Eddy Simulation turbulence model to determine the overall performance of the optimized geometry. The results indicate that the optimized bridge pier geometry reduces the time average of maximum shear stresses acting on the riverbed by approximately 5% compared to the original geometry. Furthermore, the instantaneous maximum values are reduced by around 50%. It was also concluded that the optimized geometry could reduce the potential for clean water scour without compromising the structural safety of the bridge pier by changing the original geometry cross-sectional area and the projected area in the flow direction at a very low rate (1.6%).