Aug 2026· Water· Vol 18, pp. 2081· 0 citations· 41 references
Abstract
Culverts are widely used to provide crossings over small rivers and can strongly influence flood hydraulics by controlling upstream water levels. During high flows, insufficient conveyance may cause pressurization and overtopping, with important implications for flood hazard assessment. Although computational fluid dynamics (CFD) is increasingly applied to investigate these complex hydraulic processes, systematic evaluations of its performance remain limited. This study addresses this gap by validating a three-dimensional CFD model against previously published laboratory experiments for culvert-only, weir-only and combined culvert–weir configurations under both steady (rising and receding discharge sequences) and unsteady flow conditions. Beyond benchmark validation, diagnostic analyses examined inlet region mesh resolution, inflow ramp history and turbulence closure, together with the associated outlet ventilation and attachment mechanisms. The model reproduced upstream water levels with mean absolute relative error (MARE) values ranging from 0.90% to 5.42% and captured the main stage–discharge relationships across the tested configurations. However, the experimentally observed transition from partially full to pressurized flow in the combined culvert–weir configuration was not reproduced consistently. The diagnostic analyses showed that inlet resolution influences entrance losses and post-submergence headwater, inflow history alters outlet attachment and ventilation and turbulence closure affects barrel filling and air-pocket morphology. The results indicate that CFD can reproduce water level and overtopping responses well when carefully configured, while regime transition prediction remains more uncertain because of its sensitivity to ventilation and discharge history effects.
The weir–flume combination facility is a type of river flow-measurement structure consisting of a flow weir and a Crump weir, designed to integrate flow measurement and upstream backwater regulation, while incorporating a central flume intended to provide a potential passage for aquatic organisms. This study proposes a novel combined weir–flume structure and systematically validates its hydraulic performance through integrated physical experimentation and high-fidelity numerical simulation. Laboratory tests across a flow range of 5–79 L/s revealed longitudinal water surface profiles and Froude number (Fr) distributions. The study findings show that: (1) As the flow increases, the flow regime of the combination facility transitions from flume flow to weir flow, with the critical transition point at a relative water depth of 0.885. (2) The RNG k-ε turbulence model in Flow-3D software (v11.2, Flow Science, Inc., Santa Fe, NM, USA) effectively simulates the flow movement in the weir–flume combination facility, with water depth simulation results closely matching the measured values, and the maximum relative error not exceeding 5%. (3) The Fr and flow velocity in the weir–flume combination facility first increase and then decrease along the length, forming a large, thin water layer area downstream of the facility, where both Fr and flow velocity reach their maximum values. (4) Flow measurement formulas for flume flow and weir flow are obtained through data fitting, with relative errors between the calculated values and measured flow rates being less than 3%. The present study focuses on the hydraulic performance and flow measurement capability of the proposed facility. Although the structural configuration is intended to facilitate ecological passage, its ecological effectiveness was not evaluated and requires further investigation in future studies.
Fan Yang, Gang Ling, Jichao Yang et al.· Water· 0 citations
A three-dimensional Computational Fluid Dynamics (CFD) model was employed to investigate the impact of structural protection measures on riverbanks subjected to flood flow-driven damage. Three structural approaches are applied to a case study the downstream river of Cua Dat spillway: (i) three groups of submerged groynes with varying height ratios R = 1.04, 2.13 and 3.14 of flow depth (do) to groyne height (hg), (ii) detention zones and (iii) concrete lining. Several hydraulic characteristics at near-bank flow, such as Qvortex, near-bank velocity (Vbank) and impact load (F) acting on bank protection slabs. Groups of submerged groynes redirect high-velocity flow toward the mainstream, which may jeopardize the integrity of bridge piers. The lower-submergence scenario (R = 1.04) generates maximum impact forces on the upper slab layer approximately 3.5 times greater than those induced by no protection measure. Results indicate that excavating natural detention zones along the left riverbank, in combination with concrete lining on the right riverbank, effectively reduces flood risk not only at structurally vulnerable zones but also at the bridge. These findings provide practical insights into the hydraulic performance of structural measures for riverbank stabilization in high-risk spillway environments.
Geyser eruption in urban drainage is a high-velocity discharge of an air–water mixture driven by intense air–water interactions. It is sudden, destructive and strongly non-linear, and is often associated with air entrapment, surcharge flows during intense rainfall and transient hydraulic processes, posing risks to drainage assets and surface infrastructure. A representative horizontal main pipe–vertical riser configuration is modelled using a volume of fluid (VOF) two-phase framework and a systematic numerical study is conducted of the inlet pressure head, dimensionless initial entrapped air index, Ia0, and the initial water-column height. Results identify a distinct eruption threshold: under the fixed geometry and boundary conditions considered in this study and within the tested parameter range, geyser eruption is triggered when Hin/H0 ≥ 1.33 andIa0 ≥ 3.20. As the free surface enters the upper riser, pronounced pressure spikes at PT4 and PT5 can serve as precursors. For a given inlet pressure head and the initial entrapped air condition, increasing the initial water-column height leads to higher eruption velocities, highlighting its control over eruption intensity.
You Fu, Longfei Teng, P. Qiang· Proceedings of the Instituti...· 0 citations
In some applications, compound weirs are implemented as adjustable structures that create additional resistance locally to help divert flow in rivers. To ensure proper functioning, the added resistance needs to be implemented into numerical river hydrodynamic models, which are typically constructed with 1D or 2D coarse meshes. Therefore, their effects should be defined through a simple formula to enable implementation as subgrid energy losses. This study employed an experimental approach to estimate the flow resistance of submerged compound weirs under varying flow rates and configurations. A 1D analytical method based on momentum balance at the downstream side of the weir was proposed, with a correction term included to account for neglected factors. The modeled and measured results were in strong alignment for almost all 54 cases. A uniform weir configuration with the largest weir area required a higher correction coefficient for accurate predictions. Performance testing of the model on a variety of literature data shows that this method can be applied to various kinds of weirs.
Burhan Yildiz, Wim S. J. Uijttewaal· Journal of Hydraulic Enginee...· 0 citations
Conventional full-span movable weirs may require complete lowering for sediment or debris release, reducing upstream water-level control and limiting operational efficiency. This study evaluates a smart rubber and steel (SRS) movable weir that enables selective gate operation through a one-way coupled hydraulic–structural framework using the Environmental Fluid Dynamics Code (EFDC) and MIDAS Civil. Four gate-operation scenarios and gate heights of 0.5, 1.0, 1.5, and 2.0 m were analyzed to characterize flow redistribution, hydraulic loading, gate response, longitudinal-rib performance, and the safety of anchor bolts, clamping plates, and the airbag system. Selective lowering substantially altered flow distribution, with side-gate lowering producing the most critical condition and increasing maximum velocity by approximately 267% relative to the fully raised condition at a 2.0 m gate height. Hydraulic demand became strongly localized near the lowered and adjacent raised spans, although the governing static load remained dominated by hydrostatic loading. Rib comparisons showed that redistributing stiffness through additional longitudinal stiffeners reduced stress and deformation without relying solely on gate thickening, while all component-level static checks satisfied the adopted safety criteria. The results demonstrate that integrating span-specific hydraulic redistribution with structural response provides a practical basis for structurally safe and material-efficient river-infrastructure design.
Mi Sol Kim, Jae-Hyuk Koo, Derick Gabriel Stein et al.· Sustainability· 0 citations
Mesh resolution is a central source of numerical uncertainty in two-dimensional flood modelling because it controls terrain representation, wetting–drying transitions, computational cost, and the transferability of calibrated parameters. Yet controlled evidence remains limited on whether two widely used solvers exhibit the same resolution response patterns across flood magnitudes. This study compares calibrated model configurations developed in HEC-RAS 2D version 7.0 and SMS 13.0–TUFLOW Classic for a mountainous to low-gradient reach of the Little River, Tennessee, USA, using identical terrain, land cover roughness, and hydrological boundary data. The models were calibrated with the 6–11 April 2025 event and independently validated with the 11–16 March 2026 event. A factorial experiment comprising two models, five cell sizes (15–55 ft), and five flow conditions (the observed event and Q50, Q100, Q200, and Q500 design floods) resulted in 50 simulations. The study simultaneously evaluates resolution sensitivity within each calibrated model and inter-model convergence under a common scenario matrix. Inundation extent was most resolution-sensitive during the lower-magnitude observed event, whereas inter-model extent differences decreased as flood magnitude increased. Outlet hydrographs and peak discharges were comparatively stable, but local water-depth distributions became less consistent as the mesh was coarsened, particularly in SMS-TUFLOW. HEC-RAS retained greater depth consistency, plausibly because its sub-grid property tables preserve cell-scale volume and conveyance information. Overall, mesh adequacy was output- and solver-specific, indicating that grid selection should be based on the intended hydraulic output and supported by explicit spatial stability testing.
Yasin Paşa· The Scientist· 0 citations
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