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Cases of dam failures are seen almost every year globally, and the propagation of rapidly varying unsteady flows resulting from those dam failures has significant environmental and economic consequences. A three-dimensional Computational Fluid Dynamics model was created to solve unsteady Reynolds-Averaged equations to investigate the generation and propagation of dam-break flows and reflected flood waves in the presence of a trapezoidal bottom obstacle. The dam-breaks were modelled using OpenFOAM based on the Volume of Fluid method employing the Finite Volume Method, and the performance of various Reynolds-Averaged Navier-Stokes turbulence models, including the realizable k - [epsilon], SST k - [omega] (Shear Stress Transport k - [omega]), and [v.sup.2] - f models, has been evaluated. To assess the capabilities of the different turbulence models, quantitative comparisons of numerical simulations with laboratory experiments were completed, and it was found that the SST k - [omega] model performed better in predicting the free surface profiles and negative bore propagation speeds than the realizable k - [epsilon] and [v.sup.2] - f models. Key words: 3D numerical modelling, CFD, dam-break, RANS, OpenFOAM, 1. Introduction Dam failures often result in catastrophic floods that can have a significant impact on downstream areas due to the uncontrolled release of water from reservoirs. Extreme flooding events [...]

Tailings dams (TD) are usually located in valleys that are not easily accessible and hence one global digital elevation model (DEM) is used in most of the TD breach outflow modelling studies but the challenges this impose when calibrating visco-plastic rheological models has not been fully investigated. Implications of using GeoBase DEMs for model calibration is studied by comparing it with a model that is calibrated using a merged DEM generated from multiple products. The influence of rheological parameters, roughness coefficient and sediment concentration ([C.sub.v]) on simulated variables is studied. It was concluded that when GeoBase DEM was used for back analysis of the event, physically meaningful set of rheology values could not be assigned. Flow behaviour was strongly influenced by [C.sub.v] and least influenced by Manning's values. Runout distance was more sensitive to viscosity than yield stress. Mudflow depth and arrival time increased with increase in viscosity and [C.sub.v]. Key words: tailings dam, non-Newtonian, Mount Polley, digital elevation model, land cover Les digues a rejets (DR) sont habituellement situes dans des vallees qui ne sont pas facilement accessibles et, par consequent, un modele numerique d'elevation (MNE) est utilise dans la plupart des etudes de modelisation de l'ecoulement de breches dans les DR, mais les defis que cela pose lors du calage des modeles rheologiques viscoplastiques n'ont pas ete examines a fond. Les implications de l'utilisation de MNE GeoBase pour le calage du modele sont etudiees en les comparant avec un modele dont le calage a ete fait a l'aide d'un MNE fusionne genere a partir de plusieurs operations. L'influence des parametres rheologiques, du coefficient de rugosite et de la concentration en sediments ([C.sub.v]) sur les variables simulees est etudiee. Il a ete conclu que lorsque le MNE GeoBase a ete utilise pour l'analyse retrospective de l'evenement, un ensemble de valeurs rheologiques physiquement significatives n'a pu etre attribue. Le comportement de l'ecoulement a ete fortement influence par la [C.sub.v] et moins par les valeurs de Manning. La distance de ruissellement etait plus sensible a la viscosite qu'a la limite d'elasticite. La profondeur et le temps d'arrivee de l'ecoulement de la boue augmentaient avec l'augmentation de la viscosite et de la [C.sub.v]. [Traduit par la Redaction] Mots-cles : digue a rejets, non-Newtonien, Mount Polley, modele numerique d'elevation, couverture terrestre, 1. Introduction Tailings dams (TD) are mining storage facilities constructed from waste rock to impound waste solids and water generated in a mine processing plant (Wang et al. 2014). A [...]

Large eddy simulations of an open channel bend are performed at a variety of water depths and flow rates. The results at several cross sections are decomposed into sub-cells of secondary circulation using clusters of instantaneous vortices. The strength and position of the sub-cells are then modelled using decision trees, multiple linear regression, multi-layer perceptrons, and adaptive neuro-fuzzy inference systems to obtain parametric models of secondary circulation development in a channel bend. The development of individual cells and total circulation is shown for an arbitrary flow condition using the model, as well as the dependence of all the circulation output variables on the input parameters of aspect ratio and Froude number. The positions of the sub-cells (but not their circulations) are largely independent of the Froude number, and the cross-stream position of the centre cell is found to behave linearly. The model with the best performance across all predicted variables is the ANFIS model without classification. [ABSTRACT FROM AUTHOR]

The fluid dynamics of channel confluences are highly complex due to flow separation and secondary currents. Although numerous studies in the past few decades have focused on the numerical simulation of confluence flow, deformed beds were rarely used. This study attempts to address this issue through numerical simulation of the flow behavior in an open-channel confluence flume with an equilibrium degraded bed in OpenFOAM (version 6.0) to compare the results with a flatbed. In the present study, different turbulence models, including Reynolds-Averaged Navier–Stokes (RANS), large-eddy simulation (LES), and detached eddy simulation (DES) models were performed using rigid-lid and volume-of-fluid (VoF) methods. The accuracy of the models was statistically analyzed by comparing them with observation data. The results demonstrated that the LES model had the best performance, with a minimum average normalized root-mean-square error (NRMSE) of 3% under the VoF assumption. The investigation also further illuminated the intricate interplay of vortical structures within the confluence zone. Notably, the number and behavior of vortices were found to be influenced by channel geometry and size, as well as interactions between separated shear layers. Circulation within the separation zone near the inner bank differed in rotation between the degraded and flatbed cases. [ABSTRACT FROM AUTHOR]

Many high-performance fluid dynamic models do not consider fluids in a rotating environment and often require a significant amount of computational time. The current study proposes a novel parameter-based field reconstruction convolutional neural network (PFR-CNN) approach to model the solute concentration field in rotationally influenced fluids. A new three-dimensional (3D) numerical solver, TwoLiquidMixingCoriolisFoam, was implemented within the framework of OpenFOAM to simulate effluents subjected to the influence of rotation. Subsequently, the developed numerical solver was employed to conduct numerical experiments to generate numerical data. A PFR-CNN was designed to predict the concentration fields of neutrally buoyant effluents in rotating water bodies based on the Froude number (Fr) and Rossby number (Ro). The proposed PFR-CNN was trained and validated with a train-validation dataset. The predicted concentration fields for two additional tests demonstrated the good performance of the proposed approach, and the algorithm performed better than traditional approaches. This study offers a new 3D numerical solver, and a novel PFR-CNN approach can predict solute transport subjected to the effects of rotation in few seconds, and the PFR-CNN can significantly reduce the computational costs. The study can significantly advance the ability to model flow and solute transport processes, and the proposed CNN-based approach can potentially be employed to predict the spatial distribution of any physical variable in the lentic, ocean, and earth system. [ABSTRACT FROM AUTHOR]

This paper aims to develop a robust two-dimensional coupled numerical model based on an unstructured mesh, which can simulate rapidly varying flows over an erodible bed involving wet-dry fronts that is a complex yet practically important problem. Using a modified spatial reconstruction based on the finite volume method, the well-balanced property is preserved, which is important for accurate and efficient simulation of morphological problems. In the present study, the central-upwind scheme is extended to simulation of bed erosion and sediment transport for the first time. It is demonstrated that the proposed scheme shows good accuracy and high efficiency. A modified shallow water system is adopted to improve the model. The shallow water equations, sediment transport equation and bed evolution equation are coupled in the governing system. Multiple test cases are employed to demonstrate the robustness, accuracy, and efficiency of the current model. Furthermore, with a field scale dam-break test case, the efficiency and accuracy of the central-upwind method is verified in comparison with other popular Riemann solvers. The effects of the additional source terms in the adopted modified shallow water equations are also investigated by comparing the numerical results with a laboratory study available in the literature. The proposed scheme can efficiently track wetting and drying interfaces while preserving stability in simulating the bed erosion near the wet-dry fronts. The added terms in shallow water equations can improve the accuracy of the simulation when intense sediment-exchange exists; the central-upwind method adopted in the current study shows great accuracy and efficiency compared with other popular solvers; the developed model is robust, efficient and accurate to deal with various challenging cases. Key words: dam-break flows, central-upwind method, wetting and drying, bed erosion, sediment transport, shallow water equations, finite volume method. Le present article vise a developper un solide modele numerique couple bidimensionnel partir d'un maillage non structure, capable de simuler des ecoulements variant rapidement au-dessus d'un lit de riviere erodable et dans lesquels entrent en jeu des fronts d'humectation-assechement, probleme a la fois complexe et tres concret. A l'aide d'une reconstitution spatiale modifiee basee sur la methode des volumes finis, la propriete bien equilibree est preservee, ce qui est important que la simulation de problemes morphologique soit precise et efficace. Dans la presente etude, l'utilisation du schema de type centre-amont est pour la premiere fois etendue a la simulation de l'erosion des lits et du transport de sediments. On demontre que le schema propose est tres efficace et plutot precis. On adopte une equation de Saint-Venant modifiee pour ameliorer le modele. Les equations de Saint-Venant, l'equation du transport des sediments et l'equation de Revolution du lit sont couplees a l'equation principale. De nombreux exemples sont utilises pour demontrer la solidite, la precision et l'efficacite du modele actuel. De plus, en s'appuyant sur cas reel de rupture de barrage, on verifie l'efficacite et la precision du schema de type centre-amont et on le compare a celles d'autres solveurs de Riemann couramment utilises. On etudie egalement les effets des termes sources supplementaire aux equations modifies de Saint-Venant en comparant les resultats numeriques en comparant les resultats numeriques avec ceux d'une etude de laboratoire decrite dans la litterature. Le schema propose permet de suivre efficacement les interfaces d'humectation et d'assechement tout en restant stable lorsqu'on simule l'erosion du lit a proximite des fronts d'humectation-assechement. Les termes ajoutes aux equations de Saint-Venant peuvent permettre d'ameliorer la precision de la simulation lorsqu'on est en presence d'un transfert intense de sediments. Le schema de type centre-amont adopte dans le cadre de la presente etude est tres precis et efficace, compare a d'autres solveurs souvent utilises. Le modele developpe est suffisamment solide, efficace et precis pour etre applique a divers cas complexes. [Traduit par la Redaction] Mots-cles: ecoulements produits par une rupture de barrage, schema de type centre-amont, humectation et assechement, erosion du lit d'une riviere, transport de sediments, equations de Saint-Venant, methode des volumes finis., Introduction Rapidly varying flows over a mobile bed are commonly observed in engineering applications although limited studies have been dedicated to their modeling, which is a challenging task in terms [...]