Computational and experimental analysis of flow velocity and complex vortex formation around a group of bridge piers

In this study, the flow characteristics around a group of three piers arranged in tandem were investigated both numerically and experimentally. The simulation utilised the volume of fluid (VOF) model in conjunction with the k–ɛ method (i.e., for flow turbulence representations), implemented through the ANSYS FLUENT software, to model the free-surface flow. The simulation results were validated against laboratory measurements obtained using an acoustic Doppler velocimeter. The comparative analysis revealed discrepancies between the simulated and measured maximum velocities within the investigated flow field. However, the numerical results demonstrated a distinct vortex-induced flow pattern following the first pier and throughout the vicinity of the entire pier group, which aligned reasonably well with experimental data. In the heavily narrowed spaces between the piers, simulated velocity profiles were overestimated in the free-surface region and underestimated in the areas near the bed to the mid-stream when compared to measurements. These discrepancies diminished away from the regions with intense vortices, indicating that the employed model was capable of simulating relatively less disturbed flow turbulence. Furthermore, velocity results from both simulations and measurements were compared based on velocity distributions at three different depth ratios (0.15, 0.40, and 0.62) to assess vortex characteristic around the piers. This comparison revealed consistent results between experimental and simulated data. This research contributes to a deeper understanding of flow dynamics around complex interactive pier systems, which is critical for designing stable and sustainable hydraulic structures. Furthermore, the insights gained from this study provide valuable information for engineers aiming to develop effective strategies for controlling scour and minimizing destructive vortex effects, thereby guiding the design and maintenance of sustainable infrastructure.