Three-Dimensional OpenFOAM-Based Simulation of Floating debris Transport and Accumulation at Hydraulic Structures

Floating debris accumulation in rivers is a critical hydraulic and geomorphological concern, especially during floods when large volumes of debris are mobilized and conveyed downstream (Pace et al., 2024). Debris accumulation at hydraulic structures (e.g., bridges and weirs) can markedly increase flow resistance, intensify local acceleration and turbulence, and impose excessive hydrodynamic loads, thereby threatening structural integrity and flood safety (Diehl, 1997; Ruiz-Villanueva et al., 2016). Despite numerous flood-related failures associated with floating debris , the three-dimensional processes governing debris accumulation and its interaction with complex flow fields remain insufficiently understood, limiting robust prediction and risk assessment (Braudrick and Grant, 2000; Manners et al., 2007). This study develops an open-source, three-dimensional numerical model(OpenFOAM) informed by flume experiments and elucidates the hydraulic mechanisms underlying floating debris accumulation through quantitative validation against laboratory observations.

The model incorporates experimentally observed debris-accumulation configurations and hydraulic responses (Kim, 2021; Müller et al., 2022), and reproduces debris transport pathways and accumulation processes based on controlled debris-feeding experiments (Toé et al., 2025). Model performance is evaluated across multiple accumulation scenarios through quantitative comparisons of key hydraulic variables, including water surface elevation, velocity fields, and Froude number, enabling assessment of backwater effects, local flow acceleration, and flow-regime transitions. In addition, the stability and failure of debris carpets reported by Toé et al. (2025) are numerically reproduced to examine accumulation–flow feedbacks under increasing discharge. The results demonstrate that the proposed model successfully captures the fundamental hydraulic processes governing floating debris accumulation and provides a robust framework for analyzing debris–flow interactions at hydraulic structures.
 Numerical predictions agree closely with experimental measurements, demonstrating that the model captures fundamental hydraulic mechanisms controlling debris accumulation at structures. The simulations reproduce preferential accumulation zones and temporal growth rates, resolving the coupling between three-dimensional flow structures and debris transport. Results further show that accumulation-induced flow contraction and associated near-bed shear stress amplification intensify localized turbulence and modify the near-bed flow regime, which in turn governs accumulation stability. Importantly, the spatial distribution and magnitude of bed shear stress emerge as primary determinants of transitions from stable accumulation to instability (e.g., squeezing) and eventual failure.
The proposed, experimentally validated, physics-informed model provides a reference framework for simulating floating debris transport, accumulation dynamics, and interactions with hydraulic structures. It supports quantitative assessment of debris-induced head losses and hydraulic loads, thereby informing flood-risk evaluation and the design and management of debris-prone structures.

”This work is financially supported by Korea Ministry of Climate, Energy, Environment (MCEE) as ｢Research and Development on the Technology for Securing the Water Resources Stability in Response to Future Change (RS-2024-00332494)｣.”