43 research outputs found
Discontinuous Galerkin finite element modelling of estuarine and plume dynamics
No full textEstuaries are water bodies where riverine – fresh – and marine – salty – waters meet, leading to complex mixing processes depending on a wealth of parameters and forcings. Such regions are amongst the most productive natural habitats in the world. Understanding and predicting their hydrodynamics was and still is a daunting task that is crucial for the management of the land-sea continuum, where the majority of human activities take place. The first objective of this thesis is to further develop SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model, www.climate.be/slim), a multi-scale model using the discontinuous Galerkin finite element method in order to improve its ability to represent the aforementioned flows. The stability and accuracy of SLIM’s three-dimensional baroclinic module is improved, allowing the model to tackle a wide range of estuarine flow regimes. In a second phase, the improved model is applied to the estuaries and plumes of two major rivers of the world: the Columbia (Oregon, U.S.A.) and the Congo (Central Africa) Rivers. In both cases, the computational domain covers the coastal ocean and includes the tidally-influenced part of the rivers. The stratified flows inside the estuaries are dealt with, as well as the plumes, within a single unstructured mesh exhibiting a wide range of element sizes, adapted to the geometry of the domain and the key flow features. It has been seen that cutting-edge simulation tools – going beyond the capabilities of today’s popular three-dimensional models – are needed to tackle the complex phenomena related to stratification, tides and wind stress taking place in regions of freshwater influence. For instance, the development on the continental shelf of the Columbia River plume is highly sensitive to the wind forcing, requiring relevant turbulence closure schemes, sophisticated vertical discretisation and variable horizontal resolution. As for the Congo River, the deep canyon cutting through the estuary and the continental shelf makes this region unique. Its dynamics is shown to share similarities with fjords, i.e. strong stratification and poor ventilation of deep areas, which hence exhibit almost anoxic waters.(FSA - Sciences de l'ingénieur) -- UCL, 201
Numerical study of tides in Ontario Lacus, a hydrocarbon lake on the surface of the Saturnian moon Titan
No full textIn the context of the emergence of extra-terrestrial oceanography, we adapted an existing oceanographic model, SLIM (www.climate.be/slim), to the conditions of Titan, a moon of Saturn. The tidal response of the largest southern lake at Titan's surface, namely Ontario Lacus, is simulated. SLIM solves the 2D, depth-averaged shallow water equations on an unstructured mesh using the discontinuous Galerkin finite element method, which allows for high spatial resolution wherever needed. The impact of the wind forcing, the bathymetry, and the bottom friction is also discussed. The predicted maximum tidal range is about 0.56 m in the southern part of the lake, which is more than twice as large as the previous estimates (Tokano, 2010). The patterns and magnitude of the current are also markedly different from those of previous studies: the tidal motion is not aligned with the major axis of the lake and the speed is larger nearshore. Indeed, the main tidal component rotates clockwise in an exact period of one Titan day and the tidal currents can reach 0.046 m/s close to the shores depending on the geometry and the bathymetry. Except for these specific nearshore regions, the current speed is less than 0.02 m/s. Circular patterns can be observed offshore, their rotational direction and size varying along the day
"Management of impacts as a new factor of business success: a look from The Corporate Social Responsibility "
No full textEn este trabajo se pretende hacer una sinopsis o comparación respecto a los últimos avances que ha tenido el tema de la Responsabilidad Social Empresarial, especialmente a partir del autor y filósofo francés François Vallaeys, quien ha introducido unos nuevos conceptos sobre la RSE enfocándola sobre la gestión de los impactos negativos que puede tener la empresa en el desarrollo de sus actividades, no solo en el ámbito social sino también aspectos tan importantes como el clima organizacional, los empleados, los proveedores y el mercado en general y de igual manera con el medio ambiente, apartándose de lo que ha sido el enfoque tradicional de RSE que se ha manejado en torno a los impactos que pueda tener únicamente la organización sobre el contexto en el cual desarrolla su gestión.This paper intends to make a synopsis or comparison with the latest advances in Corporate Social Responsibility, especially from the French author and philosopher François Vallaeys, who has introduced some new concepts on CSR focusing on management Of the negative impacts that the company can have in the development of its activities, not only in the social area but also as important aspects as the organizational climate, employees, suppliers and the market in general and also with the environment , Moving away from what has been the traditional CSR approach that has been managed around the impacts that can only have the organization on the context in which it develops itsPregrad
Discontinuous Galerkin modeling of the Columbia River's coupled estuary-plume dynamics
No full textThe Columbia River (CR) estuary is characterized by high river discharge and strong tides that generate high velocity flows and sharp density gradients. Its dynamics strongly affects the coastal ocean circulation. Tidal straining in turn modulates the stratification in the estuary. Simulating the hydrodynamics of the CR estuary and plume therefore requires a multi-scale model as both shelf and estuarine circulations are coupled. Such a model has to keep numerical dissipation as low as possible in order to correctly represent the plume propagation and the salinity intrusion in the estuary. Here, we show that the 3D baroclinic discontinuous Galerkin finite element model SLIM 3D is able to reproduce the main features of the CR estuary-to-ocean continuum. We introduce new vertical discretization and mode splitting that allow us to model a region characterized by complex bathymetry and sharp density and velocity gradients. Our model takes into account the major forcings, i.e. tides, surface wind stress and river discharge, on a single multi-scale grid. The simulation period covers the end of spring-early summer of 2006, a period of high river flow and strong changes in the wind regime. SLIM 3D is validated with in-situ data on the shelf and at multiple locations in the estuary and compared with an operational implementation of SELFE. The model skill in the estuary and on the shelf indicate that SLIM 3D is able to reproduce the key processes driving the river plume dynamics, such as the occurrence of bidirectional plumes or reversals of the inner shelf coastal currents.Accepted Author ManuscriptMathematical Physic
Integrated hydrodynamic and machine learning models for compound flooding prediction in a data-scarce estuarine delta
No full textFlood forecasting based on hydrodynamic modeling is an essential non-structural measure against compound flooding across the globe. With the risk increasing under climate change, all coastal areas are now in need of flood risk management strategies. Unfortunately, for local water management agencies in developing countries, building such a model is challenging due to the limited computational resources and the scarcity of observational data. We attempt to solve this issue by proposing an integrated hydrodynamic and machine learning (ML) approach to predict water level dynamics as a proxy for the risk of compound flooding in a data-scarce delta. As a case study, this integrated approach is implemented in Pontianak, the densest coastal urban area over the Kapuas River delta, Indonesia. Firstly, we build a hydrodynamic model to simulate several compound flooding scenarios. The outputs are then used to train the ML model. To obtain a robust ML model, we consider three ML algorithms, i.e., random forest (RF), multiple linear regression (MLR), and support vector machine (SVM). Our results show that the integrated scheme works well. The RF is the most accurate algorithm to model water level dynamics in the study area. Meanwhile, the ML model using the RF algorithm can predict 11 out of 17 compound flooding events during the implementation phase. It could be concluded that RF is the most appropriate algorithm to build a reliable ML model capable of estimating the river's water level dynamics within Pontianak, whose output can be used as a proxy for predicting compound flooding events in the city
A fully consistent and conservative vertically adaptive coordinate system for SLIM 3D v0.4 with an application to the thermocline oscillations of Lake Tanganyika
No full textThe discontinuous Galerkin (DG) finite element method is well suited for the modelling, with a relatively small number of elements, of three-dimensional flows exhibiting strong velocity or density gradients. Its performance can be highly enhanced by having recourse to r-adaptivity. Here, a vertical adaptive mesh method is developed for DG finite elements. This method, originally designed for finite difference schemes, is based on the vertical diffusion of the mesh nodes, with the diffusivity controlled by the density jumps at the mesh element interfaces.The mesh vertical movement is determined by means of a conservative arbitrary Lagrangian–Eulerian (ALE) formulation. Though conservativity is naturally achieved, tracer consistency is obtained by a suitable construction of the mesh vertical velocity field, which is defined in such a way that it is fully compatible with the tracer and continuity equations at a discrete level.The vertically adaptive mesh approach is implemented in the three-dimensional version of the geophysical and environmental flow Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM 3D; www.climate.be/slim). Idealised benchmarks, aimed at simulating the oscillations of a sharp thermocline, are dealt with. Then, the relevance of the vertical adaptivity technique is assessed by simulating thermocline oscillations of Lake Tanganyika. The results are compared to measured vertical profiles of temperature, showing similar stratification and outcropping events.Mathematical Physic
A coupled ecohydrodynamic model to predict algal blooms in Lake Titicaca
No full textLake Titicaca is home to a unique high-altitude ecosystem that is suffering from increasing anthropogenic pressures. It experienced its first major algal bloom in March–April 2015 that had devastating consequences in the southern shallow lake basin. Such events are expected to intensify in the future and call for a more active and quantitative management of the lake and its watershed. In this paper we describe a coupled ecohydrodynamic model to predict the lake’s water quality and, more particularly, the risk of harmful algal blooms. We have coupled a nitrogen-phytoplankton-zooplankton-detritus (NPZD) ecosystem model to the unstructured-mesh 3D hydrodynamic model SLIM. Our high-resolution multi-scale model explicitly represents the exchanges between the two basins composing the lake, through the narrow Strait of Tiquina. This allowed us to study the biophysical processes driving the entire lake over the period of January 2014 to May 2015. The model has been validated against temperature profiles at several locations throughout the lake. It correctly reproduces the seasonal temperature variations that drive the lake stratification and impact the vertical distributions of phytoplankton. Our model was able to replicate the space–time dynamics of the March–April 2015 algal bloom similarly to what was observed on satellite imagery. We believe that our multiscale ecohydrodynamic model is a promising tool to complement field observations and hence support water management in the lake and its watershed
University Social Responsibility: a systematic review and a bibliometric analysis
No full textEl propósito de este artículo es realizar una revisión sistemática y un análisis bibliométrico de la producción científica relacionada con la Responsabilidad Social Universitaria, a través de una revisión en las bases de datos Web of Science y Scopus. Los registros obtenidos fueron analizados empleando la teoría de grafos y herramientas como bibliometrix, Sci2 Tool y Gephi; además, fueron presentados en tres categorías: hegemónicos, estructurales y recientes. Los resultados permitieron identificar tres perspectivas: medición, estratégico y conexión; también muestran que este campo de estudio es relativamente joven, en el cual el autor principal es Ricardo Gaete, mientras que François Vallaeys es el más citado. Adicionalmente, la región de mayor producción en el tema es Suramérica.The purpose of this article is to perform a systematic review and a bibliometric analysis of the scientific production related to University Social Responsibility, by means of a review in the Web of Science and Scopus databases. The records obtained were analyzed using the graph theory and tools such as bibliometrix, Sci2 Tool, and Gephi. In addition, they were presented in three categories: hegemonic, structural, and recent. The results allowed to identify three perspectives: measurement, strategic, and connection. They also show that this field of study is relatively young, in which the principal author is Ricardo Gaete, while François Vallaeys is the most cited. Additionally, the region with the highest production in the subject is South America
Responsabilidad social universitaria: estudio de caso Universidad Autónoma de Manizales
No full textIntroducción: El presente estudio surgió de la necesidad de tener una línea base en términos de Responsabilidad Social Universitaria (RSU), para evaluar posteriormente el impacto de la Universidad Autónoma de Manizales en la comunidad, tomando como referencia el proceso de autoevaluación y la información adicional en términos de introducir mejoras que le permitan a la institución posicionarse como una universidad de alta calidad en la región. Este trabajo se elaboró bajo el enfoque teórico de la Responsabilidad Social Universitaria, según los impactos en los ámbitos cognitivo, social, educativo y organizacional de acuerdo con el modelo planteado por el autor François Vallaeys en el año 2008.Introduction: This study arose from the need to have a baseline in terms of University Social Responsibility (USR), to subsequently evaluate the impact of the Autonomous University of Manizales in the community, taking as a reference the self-evaluation process and the additional information in terms of introducing improvements that allow the institution to position itself as a high-quality university in the region. This work was developed under the theoretical approach of University Social Responsibility, according to the impacts in the cognitive, social, educational and organizational fields according to the model proposed by the author François Vallaeys in 2008
Modeling interactions between tides, storm surges, and river discharges in the Kapuas River delta
No full textThe Kapuas River delta is a unique estuary system on the western coast of the island of Borneo, Indonesia. Its hydrodynamics are driven by an interplay between storm surges, tides, and river discharges. These interactions are likely to be exacerbated by global warming, leading to more frequent compound flooding in the area. The mechanisms driving compound flooding events in the Kapuas River delta remain, however, poorly known. Here we attempt to fill this gap by assessing the interactions between river discharges, tides, and storm surges and how they can drive a compound inundation over the riverbanks, particularly within Pontianak, the main city along the Kapuas River. We simulated these interactions using the multi-scale hydrodynamic model SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model). Our model correctly reproduces the Kapuas River's hydrodynamics and its interactions with tides and storm surge from the Karimata Strait. We considered several extreme-scenario test cases to evaluate the impact of tide–storm–discharge interactions on the maximum water level profile from the river mouth to the upstream part of the river. Based on the maximum water level profiles, we divide the Kapuas River's stream into three zones, i.e., the tidally dominated region (from the river mouth to about 30 km upstream), the transition region (from about 30 km to about 150 km upstream), and the river-dominated region (beyond 150 km upstream). Thus, the local water management can define proper mitigation for handling compound flooding hazards along the riverbanks by using this zoning category. The model also successfully reproduced a compound flooding event in Pontianak, which occurred on 29 December 2018. For this event, the wind-generated surge appeared to be the dominant trigger
