Author(s): Wenjun Zhang
Linked Author(s):
Keywords: Woody debris large eddy simulation dynamic debris jam flow fields vorticity system
Abstract: The occurrence of extreme flood events has significantly increased due to global climate change, causing direct damage to buildings and infrastructure. This issue has gained considerable attention in efforts to mitigate its impacts. These extreme floods also transport immense amounts of woody debris into rivers, and debris jams are often trapped by bridges, contributing to over one-third of bridge failures in the United States. This highlights the critical need to investigate the influence of debris jams on bridge piers. In this study, we examined various debris jam shapes with differing sizes, side angles, and ramp lengths, based on previous experimental work, using numerical simulation methods. We applied Large Eddy Simulation (LES) with the dynamic k-model, after validating against experimental results. Additionally, we simulated the effects of debris jam shape on flow fields, vorticity structures, and bed wall shear stress. The results indicated that the velocity distribution was primarily influenced by the shape of the debris jam, particularly the side angle. The horseshoe vortex was visualized, showing that its size increased with the size of the debris jam. Furthermore, bed wall shear stress, normalized by the Shields number, was used to predict scour around the debris jam. Scour depth was found to intensify with increasing approach velocity and size of the debris jam. This study is the first to clarify the evolution of flow fields and forces on debris jams as their size increases.
Year: 2025