Using satellite imagery for studying the dynamics of the Rio de la Plata turbidity front

Both remote sensing and numerical modeling studies heavily rely on field data for calibration and validation, but they are seldom used to validate each other. In this work we used the turbidity front detected from satellite imagery to evaluate the performance of a numerical hydro-sedimentological model of the Rio de la Plata. The Rio de la Plata is a micro-tidal estuary located between Argentina and Uruguay in South America. It is approximately 280 km long and its width increases from 20 km at the inner part to 220 km at its mouth. Due to its large extension, satellite images are one of the few tools able to provide a synoptic view of the estuary. The estuary receives an annual mean flow of 22.000 m³/s from the Parana and Uruguay rivers, and 160x106 tons/yr of sediment, which are mostly cohesive sediments coming from the upper Parana River basin. The following data was available for studying the response of the system to the main forcings: daily discharges of the main tributaries from 2001 to 2017 (the mean discharge for the 2014-2017 period was 24250 m³/s); wind data every six hours from the European Centre for Medium-Range Weather Forecasts (ECMWF); CTD salinity measurements at two sites along the northern coast of the Rio de la Plata (just in front of Montevideo and approximately 40 km to the W). We used images from the MODIS-Aqua satellite mission from 2014 to 2017. The images have a spatial resolution of approximately 1 km and a daily time step, and we used the red channel reflectance (wavelength of 645 nm) to detect the turbidity front location. The turbid river water in the inner and intermediate regions of the estuary has high reflectance, while the clear seawater in the outer zone and continental shelf has negligible reflectance. This allowed us to implement an image-based, autonomous algorithm, defining the turbidity front as a reflectance level that ‘best’ separates the two reflectance regions. We analyzed the distribution of the front location over the 2014-2017 period, and found that the front location along the Uruguayan coast is more often located to the E of Montevideo, approximately 60% of the time, being the maximum eastward distance 143 km. On the other hand, we observed that the front could recede up to 70 km to the W of Montevideo. The turbidity front location along the Uruguayan coast presented statistically significant linear correlation with the Parana and Uruguay river discharges, with larger discharges being associated with positions further to the E. Regarding the wind, we observed as a general trend that positions to the W are associated with relatively weaker winds from all directions, while positions to the E show a larger scatter and are more frequently associated with stronger winds. We also observed a general trend in the data indicating that the front location along the north coast was particularly affected by winds coming from the SW and ENE directions

Methodologies for teaching an engineering subject in different countries: comparison and results

Engineering or technical degrees are difficult to teach and, consequently, have always been characterized by a large number of academic failures. Therefore, continuous assessment has been applied to classes of similar content, related to Port and Coastal Engineering during these last years in three different Universities worldwide: University of La Republica (Montevideo, Uruguay), Nova de Lisboa (Portugal) and Cadiz (Spain). This paper presents different methodologies used to teach and evaluate these courses at each University, together with the results of the evaluations of the students who were enrolled during the current and previous stages. Generally, a decrease in the number of students who abandon the classes has been noticed together with an increase in the percentage of students who pass and an improvement of their grades, except at the University Nova de Lisboa were the results have remained stable. In addition, changes experienced in the courses are discussed herein by comparing the percentage of success in the different locations. Moreover, influence of the different methodologies and the possible reasons for these changes are also presented and analysed. As a conclusion, the improvement in educational outcomes has been achieved through the concurrence of different factors: the existence of more frequent written and/or oral exams, practical examples of case studies as well as access to specific tools of new technology and to documentation specifically prepared for the classes and available online. Evidently, the above mentioned tasks require a strong commitment and great effort by the teaching staff. If human resources diminish, as it is happening in Spain and Portugal due to the budget reduction in education, two difficult questions arise: For how long will teachers’ current effort be maintained? What impact will have their complete devotion to teaching in their research performance

Simulación numérica y experimental del flujo en una confluencia

La caracterización de las estructuras turbulentas presentes aguas abajo de confluencias fluviales se ha llevado a cabo tradicionalmente en analogía con distintos procesos turbulentos estudiados en profundidad en mecánica de los fluidos. Uno de los flujos análogos que podría ser adoptado para la caracterización de estructuras turbulentas en confluencias cuyas geometrías en planta de los flujos de aproximación origina una zona de estancamiento aguas abajo de estos con un déficit de velocidad y una elevada transferencia lateral de cantidad de movimiento en la interfase de mezcla es el caso de estelas turbulentas generadas en flujos en presencia de un obstáculo. En este trabajo se detallan las simulaciones numéricas y experimentales realizadas a los fines de evaluar la conveniencia del uso de esta analogía al caracterizar flujos en presencia de un obstáculo y en una confluencia con características geométricas similares. Para ello se ha implementado un modelo numérico que permite resolver las ecuaciones que caracterizan el flujo incompresible en un dominio simplificado (flujos de aproximación paralelos) y que esta implementado en el código libre y abierto OpenFOAM(R) (Open Field Operation and Manipulation). El modelo numérico fue validado utilizando datos experimentales específicamente registrados para este estudio en un canal de sección rectangular a fondo rígido en las instalaciones del Instituto de Mecánica de los Fluidos e Ingenieria Ambiental (IMFIA), Facultad de Ingeniería,. Universidad de la República, Montevideo, Uruguay. En la etapa de validación se compararon los campos de velocidades longitudinales y los tiempos característicos de las estructuras turbulentas obtenidas en el modelo experimental y el simulado numéricamente para las dos configuraciones de flujo (flujo en presencia de un obstáculo y en una confluencia con características geométricas similares) obteniéndose un buen contraste en los resultados generados con ambos modelos (experimental y numérico). Trabajos futuros prevén la utilización del modelo numérico para evaluar los rangos de condiciones geométricas (diámetro de la nariz de la confluencia y ángulo de aproximación) y de flujo (relación de caudales y momentos de flujo) para el cual la analogía propuesta es apropiada.Fil: Pozzi Piacenza, Cecilia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Hidráulica. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Herrero, Horacio. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Hidráulica. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Furlan, Paloma. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Hidráulica. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Ragessi, Matías. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Hidráulica. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Márquez Damián, Santiago. Universidad Nacional de Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Mecánica Computacional; Argentina.Fil: López, Guillermo. Universidad de la República. Facultad de Ingeniería. Instituto de Mecánica de los Fluidos e Ingeniería Ambiental; Uruguay.Fil: Pedocchi, Francisco. Universidad de la República. Facultad de Ingeniería. Instituto de Mecánica de los Fluidos e Ingeniería Ambiental; Uruguay.Fil: Garcia, Carlos Marcelo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Hidráulica. Centro de Estudios y Tecnología del Agua; Argentina.Ingeniería Civi

Bed Morphology and Sediment Transport Under Oscillatory Flow

177 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.The experiments focused on two aspects of the bed morphology: the study of the ripple planform geometry under a broad range of flow conditions, and the effect of orbital velocities on the ripple size under long water excursions. Regarding the planform geometry of the ripples, the results showed that narrow facilities restrict the three-dimensional development of bedforms. For the case of the long water excursion experiments, the ripple size was found to initially decrease as the maximum orbital velocity was increased, as it has been reported by other authors. However, as the maximum orbital velocity was further increased anorbital ripples did not develop and instead the ripples started to increase their size. These last ripples had round crests, and do not seem to belong to the same bedform class as the sharp crested ripples usually reported in the literature.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Bed Morphology and Sediment Transport Under Oscillatory Flow

177 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.The experiments focused on two aspects of the bed morphology: the study of the ripple planform geometry under a broad range of flow conditions, and the effect of orbital velocities on the ripple size under long water excursions. Regarding the planform geometry of the ripples, the results showed that narrow facilities restrict the three-dimensional development of bedforms. For the case of the long water excursion experiments, the ripple size was found to initially decrease as the maximum orbital velocity was increased, as it has been reported by other authors. However, as the maximum orbital velocity was further increased anorbital ripples did not develop and instead the ripples started to increase their size. These last ripples had round crests, and do not seem to belong to the same bedform class as the sharp crested ripples usually reported in the literature.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Challenges for chlorophyll-a remote sensing in a highly variable turbidity estuary, an implementation with sentinel-2

Coastal waters have high ecological and economic relevance and are globally threatened by intense human activities leading to eutrophication. The decameter resolution of Sentinel-2 Multispectral Instrument (S2-MSI) provides an advantage to detect spatially heterogeneous phenomena that are limited in extent, such as harmful cyanobacterial blooms (cyanoHABs). Chlorophyll-a is typically used in remote sensing of blooms; however, it remains to be evaluated in several coastal regions of the world. The Río de la Plata estuary (South America) provides a key case study due to its highly variable concentrations of suspended sediments, and the increasing frequency of cyanoHABs. Here, we evaluate the potential and limitations of S2-MSI indices to retrieve chlorophyll-a in these optically complex waters, obtaining regional algorithms and comparing them to previously available ones. We propose an approach to follow the evolution of chlorophyll-a thresholds (10 and 24 μg/L) that can contribute to monitoring programs and early warning strategies of cyanoHABs

Estudio hidrodinámico e hidro-sedimentológico de la Bahía de Montevideo

Convenio entre la Administración Nacional de Puertos (ANP) y la Facultad de Ingeniería-Instituto de Mecánica de los Fluídos e Ingeniería Ambiental (IMFIA) a través de la Fundación Julio Ricaldoni (FJR)En este convenio se abordó el estudio de la hidrodinámica e hidro-sedimentología en la Bahía de Montevideo y recinto portuario. Metodológicamente el estudio incluye tres componentes. Por un lado el desarrollo de un modelo hidrodinámico y sedimentológico tridimensional avanzado para la costa de Montevideo que incluye además el efecto del oleaje (TELEMAC). Por otro lado la aplicación del modelo básico bidimensional hidrodinámico RMA, disponible en el IMFIA, que resuelve el flujo en la Bahía de Montevideo y zona portuaria generado por las mareas (RMA2D) y que se utiliza para el cálculo de los tiempos de residencia del agua en la Bahía. La tercera componente refiere a las mediciones de corriente que se realizaron en la boca de la Bahía de Montevideo con un equipo acústico ADCP fondeado durante varios meses. La implementación de ambos modelos numéricos considera las principales características de la dinámica del Río de la Plata que muestra una variabilidad influenciada por la marea astronómica y los eventos de marea meteorológica u ondas de tormenta. Las primeras con régimen semidiurno con desigualdades diurnas, y las segundas y de frecuencia aproximadamente semanal y de varios días de duración

Flow structure at a confluence: experimental data and the bluff body analogy

An experimental characterization of the hydrodynamics of a mixing interface at an open channel confluence is presented. In the laboratory experiments, both a confluence and a cylinder set-up were studied in order to validate the bluff body analogy, which has been proposed to characterize the mixing interface. The experimental characterization included flow visualization and the computation of the mean flow field, time scales of the coherent structures, and turbulent kinetic energy. The comparison among the two configurations confirms the validity of the analogy as similar features were found for the mean flow field and time scales of the coherent structures. However, differences in the length of the stagnation zone, the flow velocity deficit, and the turbulence intensity were observed. These differences should be taken into account when the bluff body analogy is used to characterize the confluence hydrodynamics and to quantify the mixing at the confluence interface.Fil: Herrero, Horacio Sebastian Julian. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: García, Carlos M.. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pedocchi, Francisco. Universidad de la República. Facultad de Ingeniería. Instituto de Mecánica de los Fluidos e Ingeniería Ambiental; UruguayFil: Guillermo, López. Universidad de la República. Facultad de Ingeniería. Instituto de Mecánica de los Fluidos e Ingeniería Ambiental; UruguayFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Departamento de Hidráulica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Pozzi Piacenza, Cecilia Elena. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; Argentin