Search

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]

Recent catastrophic tsunamis, such as the 2004 Indian Ocean and 2011 Tohoku events, have underscored the need for resilient coastal infrastructure. Field investigations in the aftermath of these tsunamis have consistently identified local scour around structures as a critical factor contributing to their failure. Local scour refers to the erosion or removal of sediment in the vicinity of a structure, triggered by the unsteady water flow associated with tsunami inundation. The recognition of the significance of this phenomenon, juxtaposed with the current deficiency of detailed and systematic design guidelines that incorporate the ramification of local scour, has spurred advancements in this area of research. This study has meticulously reviewed state-of-the-art studies on tsunami-induced local scour around structures. The existing design guidelines have been critically assessed, pinpointing their limitations and areas that require further elucidation. Moreover, this critical analysis delineates the current knowledge gaps and outlines prospective directions for future research endeavors aimed at enhancing the resilience of coastal infrastructure, with a particular focus on mitigating the effects of local scour. This comprehensive review aims to deepen the understanding of tsunami-induced local scour and promote more effective, evidence-based design strategies to mitigate the risk of structural failure in high-risk coastal areas. [ABSTRACT FROM AUTHOR]