Análisis de los modelos 3D para la simulación de flujo en aguas de transición

Actualmente, las aguas de transición, definidas por la Directiva Marco del Agua 2000/60/CE como masas de agua superficial próximas a la desembocadura de los ríos que son parcialmente salinas como consecuencia de su proximidad a las aguas costeras, pero que reciben una notable influencia de flujos de agua dulce, están siendo objeto de numerosos estudios dirigidos a su rehabilitación y conservación. Consideradas hoy en día como valiosos hábitats, es necesario contar con las herramientas adecuadas para llevar a cabo su gestión correctamente. Una de las partes más importantes del estudio de estas áreas consiste en conocer su hidrodinámica, para lo cual cada vez está más extendido el uso de modelos numéricos. En este artículo se analiza las situaciones que pueden inducir flujo tridimensional en las aguas de transición y se hace una revisión de los modelos tridimensionales existentes actualmente para el estudio hidrodinámico de las mismas. Como resumen de esta revisión se elabora una tabla en la que se comparan los modelos atendiendo a su idoneidad para representar las características de estas masas de aguas

Modeling Nonconfined Density Currents Using 3D Hydrodynamic Models

Density currents generated by marine brine discharges, e.g., from desalination plants, can have a negative impact on marine ecosystems. It is therefore important to accurately predict their behavior. Predictions are often made using computational hydrodynamic models, which should be validated using field or laboratory measurements. This paper focuses on the setup and validation of three-dimensional (3D) models for estimating the transport and mixing processes that occur in these types of flows. Through a comprehensive sensitivity analysis based on the reproduction of several laboratory-generated density currents, a set of recommendations are made regarding the modeling aspects, including the domain discretization, the treatment of momentum at the density current source, the hydrostatic hypothesis and the selection of turbulence closure models. Finally, the proposed numerical model setup is validated using different experimental data showing good agreement in terms of the main variables considered: errors of less than 1.3% for dilution and of 6% for velocity. This study serves as a first step toward the full validation of these 3D hydrodynamic models for the simulation of field-scale density currents.This study was partially funded by the Ministry of Economy and Competitiveness (MINECO) under research project TRA2011-28900 (PLVMA3D). B. Pérez-Díaz would like to thank MINECO for providing funding under the FPI Program (research fellowship, reference number BES-2012-053693) and the Coasts and Ocean Group of HRWallingford for their assistance with numerical tasks

Influence of postoperative complications on long-term survival in liver transplant patients

Background: Liver transplant (LT) is a complex procedure with frequent postoperative complications. In other surgical procedures such as gastrectomy, esophagectomy or resection of liver metastases, these complications are associated with poorer long-term survival. It is possible this happens in LT but there are not enough data to establish this relationship. Aim: To analyze the possible influence of postoperative complications on long-term survival and the ability of the comprehensive complication index (CCI) to predict this. Methods: Retrospective study in a tertiary-level university hospital. The 164 participants were all patients who received a LT from January 2012 to July 2019. The follow-up was done in the hospital until the end of the study or death. Comorbidity and risk after transplantation were calculated using the Charlson and balance of risk (BAR) scores, respectively. Postoperative complications were graded according to the Clavien-Dindo classification and the CCI. To assess the CCI cut-off value with greater prognostic accuracy a receiver operating characteristic (ROC) curve was built, with calculation of the area under the curve (AUC). Overall survival was estimated according to the Kaplan-Meier test and log-rank test. Groups were compared by the Mann-Whitney test. For the multivariable analysis the Cox regression was used. Results: The mean follow-up time of the cohort was 37.76 (SD = 24.5) mo. A ROC curve of CCI with 5-year survival was built. The AUC was 0.826 (0.730-0.922), P 33.5 (33.5 = median CCI value) showed estimated 5-year survival was 57.4 and 45.71 months, respectively (log-rank < 0.0001). Dividing patients according to the mode CCI value (20.9) showed an estimated 5-year survival of 60 mo for a CCI below 20.9 vs 57 mo for a CCI above 20.9 (log-rank = 0.147). The univariate analysis did not show any association between individual complications and long-term survival. A multivariate analysis was carried out to analyse the possible influence of CCI, Charlson comorbidity index, BAR and hepatocellular carcinoma on survival. Only the CCI score showed significant influence on long-term survival. Conclusion: A complicated postoperative period - well-defined by means of the CCI score - can influence not only short-term survival, but also long-term survival

On the sensitivity of tidal network characterization to power law estimation

ABSTRACT. Long-term simulations (3000 yr) of an idealized basin using different tidal ranges (1, 2 and 3 m) and grain sizes (120, 480 and 960 μm) have been performed in order to cover a range of hydrodynamic and sedimentary conditions. Two different cell sizes (50 and 100 m) have been used to study the impact of cell size on tidal network development. The probability distributions of the drainage area and the drainage volume have been computed for every simulation (during an ebb and a flood phase). Power law distributions are observed in drainage area and drainage volume distribution. As an objective estimation of the exponent of a power law is an open issue, different approaches (linear binning, normalized logarithmic binning, cumulative distribution function and maximum likelihood) proposed by White et al. (2008) to estimate the exponent have been used to carry out a sensitivity analysis. Our findings indicate that although all methods results in high and significant correlation coefficients, more work is needed to develop a universal, objective estimation of the exponent

Predicción probabilística de trayectorias de derrames de hidrocarburos a medio-largo plazo en el Golfo de Vizcaya

El presente trabajo ha sido parcialmente financiado por el Ministerio de Ciencia, Innovación y Universidades en el marco del proyecto OILHAZARD3D (TRA2017-89164-R

Characterizing storm-induced coastal change hazards along the United States West Coast

Traditional methods to assess the probability of storm-induced erosion and flooding from extreme water levels have limited use along the U.S. West Coast where swell dominates erosion and storm surge is limited. This effort presents methodology to assess the probability of erosion and flooding for the U.S. West Coast from extreme total water levels (TWLs), but the approach is applicable to coastal settings worldwide. TWLs were derived from 61 years of wave and water level data at shore-perpendicular transects every 100-m along open coast shorelines. At each location, wave data from the Global Ocean Waves model were downscaled to the nearshore and used to empirically calculate wave run-up. Tides were simulated using the Oregon State University?s tidal data inversion model and non-tidal residuals were calculated from sea-surface temperature and pressure anomalies. Wave run-up was combined with still water levels to generate hourly TWL estimates and extreme TWLs for multiple return periods. Extremes were compared to onshore morphology to determine erosion hazards and define the probability of collision, overwash, and inundation

LOW-COAST: hacia un sistema de monitorización de topo-batimetrías de bajo coste

Se agradece la financiación parcial de los proyectos “SISTEMA INTEGRADO DE PREDICCIÓN PROBABILÍSTICA DE INUNDACIÓN Y EROSIÓN EN PLAYAS” de SODERCAN y “EQUIPAMIENTO PARA MONITORIZACIÓN CON DRONES DE TOPO-BATIMETRÍAS EN PLAYAS Y ESTUARIOS” del Gobierno de Cantabria

Estudio de los impactos en la costa española por efecto del cambio climático

Ponencia presentada en: IV Congreso de la Asociación Española de Climatología "El Clima entre el Mar y la Montaña", celebrado en Santander del 2 al 5 de noviembre de 2004.[ES]En este artículo se presenta el Estudio de investigación sobre impactos en la costa española por efecto del cambio climático, que la Dirección General de Calidad y Evaluación Ambiental del Ministerio de Medio Ambiente, a través de la Oficina Española del Cambio Climático, ha encargado a la Universidad de Cantabria. Este trabajo se presenta como resumen de dicho Estudio y es el primero de los cuatro artículos que se presentan en este congreso, cubriendo los restantes aspectos científico-técnicos de diversas partes del Estudio.[EN]The effects of climate change on the Spanish coast are analyzed in a Project leaded by the University of Cantabria and funded by the Spanish Agency of Climate Change (Ministry of Environment). This work is presented as a summary of the Project and is one of the four papers presented in this Conference. The three companion papers cover several scientific aspects of the study

Scaling properties of tidal networks

A new methodology is developed to extract tidal network from hydrodynamic conditions, and use data derived from numerical modeling or field observations to test the hypothesis that tidal networks are characterized by scale-invariant properties. Different tidal network configurations have been obtained from long-term numerical simulations in an idealized basin. These simulations show the influence of hydrodynamic conditions (tidal range, TR) and sediment (grain size sediment, D50) on the final configuration of the network. One of the signatures of scale-invariant behavior is related to the presence of a power law relationship in the probability distribution of geometrical characteristics. For each model configuration and field site, the probability distribution of drainage area and the drainage volume has been calculated, and in both cases tidal networks show scale-invariant characteristics. After assessing the sensitivity of the results, an energy expenditure analysis shows that tidal basins evolve toward a state with less morphodynamic activity, with a lower energy expenditure compare with the initial state

Desarrollo de un modelo hidrodinámico tridimensional para el estudio de la propagación de ondas largas en estuarios y zonas someras

En la presente tesis se analizan los aspectos teóricos y prácticos necesarios para el desarrollo de un modelo numérico tridimensional válido para los estuarios típicos del Norte de España, cuyas características principales son la existencia de importantes gradientes de profundidad, , y de zonas que se inundan y se secan periódicamente debido al efecto de la marea astronómica. De la revisión del estado del conocimiento sobre modelado hidrodinámico tridimensional en zonas someras, se ha concluido que aunque existen varios modelos tridimensionales propuestos para estuarios, ninguno está preparado para su aplicación en los casos de estudio de esta tesis. La anterior aseveración está principalmente relacionada con tres temas fundamentales: sistema de coordenadas, representación de la turbulencia y simulación de la inundación - secado del dominio de cálculo. Se ha investigado con detalle estos aspectos y como resultado se ha desarrollado un modelo que incluye el resultado de la investigación realizada y que ha sido validado tanto con soluciones analíticas, como con datos de laboratorio y de campo