COLLECTIONS

Documents published in Scipedia

• Experimental study of subcritical dividing flow in an equal-width four-branch junction

  L. Nanía, M. Gómez, J. Dolz, P. Comas, J. Pomares

  Journal of hydraulic engineering (2011). Vol. 137 (10), pp. 1-8

  
  

  Abstract

  An experimental study of the subcritical dividing flow in an equal-width, four-branch junction with two inflows and two outflows is presented. A brief description of the flow characteristics is given. From the analysis of test data, a linear relationship among five nondimensional parameters, including inflow ratio, outflow ratio, Froude number of inflow in one direction, outflow depth ratio, and outflow aspect ratio, is proposed and proven to successfully predict the flow distribution in the junction. It can be used to solve the dividing flow problem in a street junction, and it can be included as a part of a numerical model of a street network involving subcritical flows.

  Abstract
  An experimental study of the subcritical dividing flow in an equal-width, four-branch junction with two inflows and two outflows is presented. A brief description of the flow [...]

  • 3
  •  read

• Experimental and numerical modelling of symmetrical four-branch supercritical cross junction flow

  L. Nanía, M. Gómez, J. Dolz, A. León

  Journal of Hydrology Engineering (2010). Vol. 48 (6), pp. 826-827

  
  

  Abstract

  The discussers congratulate the authors for their work and would like to raise some questions and comments about their results ans statements. The papers compares the computed with the measured flow depths for five flow configurations and the computed with the measured discharges for more than 200 configurations. The authors found discrepancies concerning the prediction of the location and the thickness of the oblique jumps mainly because these are set on one cell in the numerical model.

  Abstract
  The discussers congratulate the authors for their work and would like to raise some questions and comments about their results ans statements. The papers compares the computed [...]

  • 0
  •  read

• ASAR polarimetric, multi-incidence angle and multitemporal characterization of Doñana wetlands for flood extent monitoring

  B. Martí-Cardona, C. López-Martínez, J. Dolz, E. Bladé

  Remote Sensing of Environment (2010). Vol. 114 (11), pp. 2802-2815

  
  

  Abstract

  Doñana National Park wetlands, in South West Spain, undergo yearly cycles of inundation and drying out. During the hydrological year 2006–2007, 43 ASAR/Envisat images of Doñana, mostly in HH and VV polarizations, were acquired with the aim to monitor the flood extent evolution during an entire flooding cycle. The images were ordered in the seven ASAR incidence angles, also referred to as swaths, to achieve high observation frequency. In this study, backscattering temporal signatures of the main land cover types in Doñana were obtained for the different incidence angles and polarizations. Plots showing the σ0HH/σ0VV ratio behavior were also produced. The signatures were analyzed with the aid of miscellaneous site data in order to identify the effect of the flooding on the backscattering. Conclusions on the feasibility to discriminate emerged versus flooded land are derived for the different incidence angles, land cover types and phenological stages: intermediate incidence angles (ASAR IS3 and IS4) came up as the most appropriate single swaths to discriminate open water surface from smooth bare soil in the marshland deepest areas. Flood mapping in pasture lands, the most elevated regions, is feasible at steep to mid incidence angles (ASAR IS1 to IS4). In the medium elevation zones, colonized by large helophytes, shallow incidence angles (ASAR IS6 and IS7) enable more accurate flood delineation during the vegetation growing phase. Since Doñana land covers require different observation swaths for flood detection, the composition of different incidence angle images close in time provides the optimum flood mapping. Such composition is possible four times per ASAR 35-day orbit cycle, using pairs of 12-h apart IS1/IS6 and IS2/IS5 Doñana images.

  Abstract
  Doñana National Park wetlands, in South West Spain, undergo yearly cycles of inundation and drying out. During the hydrological year 2006–2007, 43 ASAR/Envisat [...]

  • 2
  •  read

• Temporal variability in the thermal regime of the lower Ebro River (Spain) and alteration due to anthropogenic factors

  J. Prats, R. Val, J. Armengol, J. Dolz

  Journal of Hydrology (2010). Vol. 387 (1-2), pp. 105-118

  
  

  Abstract

  The Ebro River is one of the longest rivers in Spain and it also has the greatest discharge. Its lower part is highly regulated and includes a system of three reservoirs (Mequinensa, Riba-roja and Flix). The water temperature is altered because of the release of hypolimnetic water and the use of water for cooling at the Ascó nuclear power plant. The thermal regime of the lower Ebro River on different time scales and the changes caused by anthropogenic factors, especially the system of reservoirs and the thermal effluent of the nuclear power plant, have been studied by installing a net of water temperature measuring stations and by using historical water temperature data provided by the thermal power plant at Escatrón. An increase of 2.3ºC in the mean annual water temperature could be demonstrated in the period 1955–2000 at this site. The effects of the system of reservoirs and of the nuclear power plant were the usual for this kind of structures and could be detected many kilometres downstream. In the summer, the cooling effect of the reservoirs and the warming effect of the nuclear power plant compensated each other. In winter, the warming effect of both summed up

  Abstract
  The Ebro River is one of the longest rivers in Spain and it also has the greatest discharge. Its lower part is highly regulated and includes a system of three reservoirs (Mequinensa, [...]

  • 2
  •  read

• Developing Flow Region and Pressure Fluctuations on Steeply Sloping Stepped Spillways

  A. Amador, M. Juny, J. Dolz

  Journal of Hydrology Engineering (2009). Vol. 135 (12), pp. 1092-1100

  
  

  Abstract

  The hydrodynamic pressure field is important for the design and safety of steeply sloping stepped spillways, which are typically designed for considerably lower maximum specific discharges than smooth spillways. The hydraulic performance of stepped spillways at high velocities may compromise its use due to major concern with safety against cavitation damage. Hydraulic model investigations were conducted in different large-size stepped chutes to characterize the nonaerated flow region which is potentially prone to cavitation damage and the pressure field acting on the step faces. The clear water depths and energy dissipation in the developing flow region are described in terms of integral measures of the turbulent boundary layer. Expressions for the location of and the flow depth at the inception point of air entrainment are derived. Pressure distributions on the horizontal and vertical faces of the step along the spillway are presented. Measurements indicated a different behavior of the pressure field in the aerated and nonaerated flow region. The mean and fluctuating pressure coefficients along the spillway are approximated by a regression function. The vertical face near the outer step edge close to the inception point of air entrainment is identified as a critical region for predicting cavitation inception in flow over stepped spillways. From the analysis of the pressure fluctuations in that region a maximum velocity of 15 m/s is proposed as a criterion to avoid extreme negative pressures in typical prototype steeply sloping stepped spillways, eventually leading to the occurrence of cavitation in the nonaerated flow.

  Abstract
  The hydrodynamic pressure field is important for the design and safety of steeply sloping stepped spillways, which are typically designed for considerably lower maximum specific [...]

  • 1
  •  read

• Variabilidad temporal en el comportamiento hidráulico del curso inferior del río Ebro

  J. Prats, J. Dolz, J. Armengol

  Ingeniería del agua (2009). Vol. 16 (4), pp. 259-272

  
  

  Abstract

  La presencia de los embalses de Mequinenza, Riba-Roja y Flix en el tramo inferior del río Ebro ha dado lugar a una serie de alteraciones (reducción de la entidad y frecuencia de las avenidas, estabilización de caudales, etc.) que han favorecido el desarrollo de macrófitos sumergidos. La viabilidad diaria y anual del régimen de caudales del tramo inferior del río Ebro como consecuencia de la regulación ejercida por los embalses se analiza en este trabajo. Los principales efectos son: importantes variaciones diarias de caudal, un menor caudal los fines de semana y la estabilización de los caudales mínimos. Asimismo, se analiza la influencia de la proliferación de macrófitos en el comportamiento hidráulico del río. En el período estudiado (200-2006) el río presentó dos tipos de comportamiento hidráulico: un comportamiento que puede considerarse como ordinario, con el cauce limpio, y otro más lento, caracterizado por menores velocidades y mayores calados para un mismo caudal. Este segundo comportamiento coincidió con épocas de sequía, con caudales bajos durante gran parte del año y proliferación de macrófitos. El paso del comportamiento lento al comportamiento ordinario se produce con avenidas importantes, que tienen el poder suficiente para arrastrar a los macrófitos.

  Abstract
  La presencia de los embalses de Mequinenza, Riba-Roja y Flix en el tramo inferior del río Ebro ha dado lugar a una serie de alteraciones (reducción de la entidad [...]

  • 0
  •  read

• Dam wall break simulation by means of a high resolution algorithm applied to the La Parota dam, Guerrero, Mexico

  M. Arganis, E. Bladé, J. Dolz, M. Juny, O. Fuentes, V. Franco, F. Luna-Cruz

  Ingeniería Hidráulica en México (2009). Vol. XXIV (3), pp. 101-106

  
  

  Abstract

  This document presents a dam wall break simulation of the La Parota hydropower project in Guerrero, Mexico, by means of the CARPA system, which is based in a 2D WAF-TVD (Weight Averaged Flux-Total Variation Diminishing) high resolution finite volume numerical scheme. With the results, it is possible to produce maps containing water depth, flow velocity, and affected zones, which are useful in the civil protection field.

  Abstract
  This document presents a dam wall break simulation of the La Parota hydropower project in Guerrero, Mexico, by means of the CARPA system, which is based in a 2D WAF-TVD (Weight [...]

  • 5
  •  read

• L'abastament d'aigua a Catalunya i la seva garantia

  J. Armengol, J. Dolz

  Nota d'economia: revista d'economia catalana i de sector públic (2009). Vol. 93-94, pp. 127-139

  
  

  • 1
  •  read

• Genetic programming and standardization in water temperature modelling

  M. Arganis, R. Val, J. Prats, K. Rodríguez, R. Domínguez, J. Dolz

  Advances in civil engineering (2009). Vol. 2009 (35960), pp. 1-10

  
  

  Abstract

  An application of Genetic Programming (an evolutionary computational tool) without and with standardization data is presented with the aim of modeling the behavior of the water temperature in a river in terms of meteorological variables that are easily measured, to explore their explanatory power and to emphasize the utility of the standardization of variables in order to reduce the effect of those with large variance. Recorded data corresponding to the water temperature behavior at the Ebro River, Spain, are used as analysis case, showing a performance improvement on the developed model when data are standardized. This improvement is reflected in a reduction of the mean square error. Finally, the models obtained in this document were applied to estimate the water temperature in 2004, in order to provide evidence about their applicability to forecasting purposes.

  Abstract
  An application of Genetic Programming (an evolutionary computational tool) without and with standardization data is presented with the aim of modeling the behavior of the [...]

  • 1
  •  read

• Preserving steady-state in one-dimensional finite-volume computations of river flow

  E. Bladé, M. Gómez, M. Sánchez-Juny, J. Dolz

  Journal of Hydrology Engineering (2008). Vol. 134 (9), pp. 1343-1347

  
  

  Abstract

  When using finite-volume methods and the conservative form of the Saint Venant equations in one-dimensional flow computations, it is important to establish the correct balance between the discretized flux vector and the geometric source terms. Over the last few years various improvements to numerical schemes have been presented to achieve this correct balance, focusing on the capability to simulate water at rest on irregular geometries (C-property). In this paper it is shown that common schemes can lead to energy-violating solutions in the case of steady flow. We present developments based on the Roe TVD finite-volume scheme for one-dimensional Saint Venant equations, which results in a method that not only satisfies the C-property, but also preserves the correct steady flow when stationary boundary conditions are used. We also present a totally irregular channel test case for the verification of the method.

  Abstract
  When using finite-volume methods and the conservative form of the Saint Venant equations in one-dimensional flow computations, it is important to establish the correct balance [...]

  • 2
  •  read