P. Amparo López-Jiménez

Performance assessment of OpenFOAM and FLOW-3D in the numerical modeling of a low Reynolds number hydraulic jump

A comparative performance analysis of the CFD platforms OpenFOAM and FLOW-3D is presented, focusing on a 3D swirling turbulent flow: a steady hydraulic jump at low Reynolds number. Turbulence is treated using RANS approach RNG k-e. A Volume Of Fluid (VOF) method is used to track the air-water interface, consequently aeration is modeled using an Eulerian-Eulerian approach. Structured meshes of cubic elements are used to discretize the channel geometry. The numerical model accuracy is assessed comparing representative hydraulic jump variables (sequent depth ratio, roller length, mean velocity profiles, velocity decay or free surface profile) to experimental data. The model results are also compared to previous studies to broaden the result validation. Both codes reproduced the phenomenon under study concurring with experimental data, although special care must be taken when swirling flows occur. Both models can be used to reproduce the hydraulic performance of energy dissipation structures at low Reynolds numbers. Two CFD models: OpenFOAM and FLOW-3D for hydraulic jump in low Reynolds numbers.Representative variables are compared for the two CFD results and experimental data.The model results are also compared to previous studies with good agreement.Both CFD codes had good behavior, but special care is required with swirling flows.A quantification of both models accuracy relating to studied variables is proposed.

An overview of leaks and intrusion for different pipe materials and failures

Most leak management methods are focused on quantifying water losses, directly related to energy and resource waste. In this research work, a comprehensive review on relationship and modelling between pipe leaks, materials, and type of failures is presented. Information necessary to study the main defects of pipe materials has been compiled and the different causes of pipe failures were reviewed and analysed. As a result, types of failures were identified depending on the pipe surrounding, pipe material and mechanisms and stresses that support the pipes. A deep focus of the leak problem is presented, analysing intrusion flows and the related pressure variation using the volume through simple orifices with fixed and variable discharge area: Fixed And Variable Area Discharge (FAVAD theory). Finally, a new relationship is proposed between pipe defects and discharge coefficients, depending on the flow through failures (induced by leaks or intrusions).

Optimization of Retention Ponds to Improve the Drainage System Elasticity for Water-Energy Nexus

The purpose of this paper is to investigate the optimization of retention ponds for energy production by a low-head hydropower converter towards smart water grids and new flood adaptation solutions. Flood drainage systems are infrastructures essential in urban areas to control floods, which include retention ponds that can be used as innovative solutions adapted to climate changes and smart water grids to produce energy in a near future and to improve the drainage system elasticity. A catchment-scale water/energy management model is used for designing solutions by defining the characteristics of the urban area and the hydropower converters. The study area is based on Alcântara zone, in a district of Lisbon, a specific down-town zone close to the Tagus river, which has the backwater sea tidal influence. A solution based on the catchment of this area for extreme values of runoff induced by a significant climate changes event in these last years is analysed and then optimized in terms of energy production for different characteristic parameters. Finally, results are shown and discussed to reveal the most suitable solutions.

Modified Affinity Laws in Hydraulic Machines towards the Best Efficiency Line

The development of hydraulic and optimization models in water networks analyses to improve the sustainability and efficiency through the installation of micro or pico hydropower is swelling. Hydraulic machines involved in these models have to operate with different rotational speed, in order that in each instant to maximize the recovered energy. When the changes of rotational speed are determined using affinity laws, the errors can be significant. Detailed analyses are developed in this research through experimental tests to validate and propose new affinity laws in different reaction turbomachines. Once the errors have been analyzed, a methodology to modify the affinity laws is applied to radial and axial turbines. An empirical method to obtain the Best Efficiency Line (BEL) in proposed (i.e., based on all the Best Efficiency Points (BEPs) for different flows). When the experimental measurements and the calculated values by the empirical method are compared, the mean errors are reduced 81.81%, 50%, and 86.67% for flow, head, and efficiency parameters, respectively. The knowledge of BEL allows managers to define the operation rules to reach the BEP for each flow, improving the energy efficiency in the optimization strategies to be adopted.

Design strategy to maximize recovery energy towards smart water grids: case study

ABSTRACT Water distribution networks (WDNs) appear as a new opportunity to generate clean energy using pumps working as turbines (PATs) instead of pressure reduction valves (PRVs). This research presents a strategy for maximizing the recovered energy, and the development of a deep feasibility analysis, enabling the selection of the best scenario and operation mode. A design for a strategy to create an acceptable PAT working in a water distribution network and maximizing energy production, without affecting the water distribution service, is presented. The characteristic parameters of the system are described, evaluating efficiency, capabilities, reliability and sustainability. In addition, an economic analysis of the project was made to evaluate the viability of PAT implementation. The total energy production in this case study was 485 MW h/year; and the feasibility indexes, internal rate of return, benefit/cost ratio and payback period were 0.79, 8.2 and 2 years, respectively.

Modelo analítico para el cálculo de distribuciones de velocidad laterales en secciones tipo potencial-ley

RESUMEN La modelización hidráulica de calados y velocidades de flujo, en cauces con secciones que admiten una representación de tipo potencial, se destaca por su versatilidad, permitiendo su utilización en numerosas aplicaciones prácticas tanto en canales naturales como artificiales. El cálculo de las variables hidráulicas (calado y velocidad media) ha sido ampliamente estudiado para este tipo de secciones. Sin embargo, en la literatura técnica no se han encontrado estudios que muestren la variación de estas magnitudes a lo largo de la sección transversal. El conocimiento de esta variación permite desarrollar estudios (ejemplo: conocer de manera aproximada los daños en diferentes zonas de la sección, analizar el transporte de sedimentos, estudiar los procesos de erosión u otras aplicaciones en hidráulica fluvial). Presentamos una metodología que permite el cálculo de las variables hidráulicas en cualquier zona de una sección tipo potencial. La metodología es aplicada a secciones simétricas, comparando los resultados generados con los obtenidos por diferentes códigos hidráulicos computacionales ampliamente aceptados por la comunidad científica (p-e- CES, HEC-RAS e IBER). Las predicciones de los parámetros hidráulicos obtenidas (usando la formulación explícita descrita en este artículo) presentan errores muy bajos, en comparación con otros modelos con mayor costo computacional. Estos errores alcanzan un valor promedio para la raíz del error cuadrático medio (RMSE) en el cálculo de la distribución lateral de velocidades de 0.13 y de 0.05, en el cálculo de la relación de velocidades respecto a la velocidad media. Estos valores indican una validación muy satisfactoria para las secciones simétricas analizadas.