Three-dimensional large eddy simulation of hydrodynamics in multi-pier tandem bridge systems

The wake flow generated by tandem bridge piers significantly interferes with downstream flow fields, resulting in complex hydrodynamic interactions that impact structural safety and durability. This study employs large eddy simulation (LES) to investigate the three-dimensional hydrodynamic characteristics of eight equally spaced tandem bridge piers under varying flow velocities (0.5-1.5 m/s), spacing ratios (1.5-3.5), and pier numbers (2-10). The results indicate that, under typical conditions, the upstream piers exhibit the highest pressure, which decreases along the flow direction, while the pressure extrema of downstream piers shift laterally. The velocity distribution is asymmetric, and vortex structures evolve from high-intensity small scales to moderate expansion and low-intensity diffusion. The lift coefficient fluctuates periodically with spatial lag, and the drag coefficient shows complex variations, including negative drag on some piers. The downstream vortex shedding frequency decreases, accompanied by multifrequency resonance. Increasing flow velocity stabilizes lift responses for upstream and midstream piers, with the main vortex shedding frequency increasing most in the upstream region and multifrequency phenomena shifting upstream. Larger spacing ratios reduce flow interference, enhance vortex shedding frequencies upstream, and strengthen multifrequency resonance, with triple-frequency resonance observed at terminal piers. An increase in the number of piers improves flow field stability, reduces peak lift, and decreases the occurrence of negative drag. These findings provide theoretical support for bridge monitoring and protection.