One of the main factors contributing to water scarcity is water loss in water distribution systems, which mainly arises from a lack of adequate knowledge in the design process, optimization of water availability, and poor maintenance/management of the system. Thus, from the perspective of sustainable and integrated management of water resources, it is essential to enhance system efficiency by monitoring existing system elements and enhancing network maintenance/management practices. The current study establishes a smart water grid (SWG) with a digital twin (DT) for a water infrastructure to improve monitoring, management, and system efficiency. Such a tool allows live monitoring of system components, which can analyze different scenarios and variables, such as pressures, operating devices, regulation of different valves, and head-loss factors. The current study explores a case study in which local constraints amplify significant water losses. It develops and examines the DT model’s application in the Gaula water distribution network (WDN) in Madeira Island, Portugal. The developed methodology resulted in a significant potential reduction in real water losses, which presented a huge value of 434,273 m³ (~80%) and significantly improved system efficiency. The result shows a meaningful economic benefit, with savings of about EUR 165k in water loss volume with limiting pressures above the regulatory maximum of 60 m w.c. after the district metered area (DMA) sectorization and the requalification of the network. Hence, only 40% of the total annual volume, concerning the status quo situation, is necessary to supply the demand. The infrastructure leakage index measures the existing real losses and the reduction potential, reaching a value of 21.15, much higher than the recommended value of 4, revealing the great potential for improving the system efficiency using the proposed methodology.

The Hydrostatic Pressure Machine (HPM) is a novel energy converter for micro and pico hydropower that becomes very suitable for installation in channels with very low head, where conventional hydraulic turbines are inadequate or too expensive. Although this technology has been studied through several experimental tests and also by numerical simulations, open source flow solvers have not been used yet. The research team on Computational Fluid Mechanics of IMFIA- Universidad de la República (Uruguay) has been developing a CFD open source solver named caffa3d, which has obtained great results in a few international challenges, although it has not been used yet for free surface flows or turbomachinery simulations. The present work shows the contributions made within caffa3d in order to enable its use for simulating a HPM. The Large Eddy Simulation (LES) method is used to model the turbulence structures of the flow. Sliding Mesh (SM) and Volume of Fluid (VOF) methods were chosen respectively to resolve the rotation of the wheel and the position of the free surface. The SM module was already validated in the past, but the VOF module needed to be validated in the present work through the simulation of free surface over a semicylindrical dam. Finally, the performance of a small 12-straight-blade HPM was simulated with caffa3d, with quite satisfactory results. Some issues of the solver yet need to be solved before other HPM with more complex designs could be studied.

The open source and freely available fluid flow solver named caffa3d was adapted to simulate the performance of a medium-scale Hydrostatic Pressure Machine (HPM) with straight radial blades, which had been previously tested in a laboratory facility. A fully detailed explanation of the code caffa3d is not intended to be included in this paper, but some of its main characteristics are mentioned for completeness. In addition, convergence and grid sensitivity analysis were performed in order to assess the adequacy of the model. Evolution of instantaneous power over a few turns of the HPM shows typical blade pass frequency for all operating discharges and another oscillatory phenomena at rotating frequency for higher discharges. The Power—Discharge and Efficiency—Discharge curves obtained from the simulations present a good correlation with the experimental curves, up to the discharge value corresponding to the maximum power of the HPM. The comparison error in power and efficiency remained below 6% for discharge lower than 97.8 L/s. For higher discharge, the flow through the HPM becomes very unsteady, with big eddy structures, underfilling of the buckets and recirculation down to the entry of the channel, significantly reducing the generated power. This behaviour was also observed during the previous experiments. In the present work, the foundations for the study of other types of turbines with caffa3d are laid.

La instalación en Uruguay de una planta de producción industrial aguas abajo de una central hidroeléctrica ha generado nuevos desafíos en la operación de esta central. En particular, para cumplir con requerimientos de la operación de la planta, es necesario asegurar el pasaje ininterrumpido de un caudal mínimo de agua a través de la represa, aún en condiciones de salto reducido. Por este motivo, el operador de la central hidroeléctrica manifestó su interés en estudiar los efectos de la operación de las turbinas, con saltos menores al mínimo de diseño. Las turbinas de la central son de tipo Kaplan, de potencia máxima 38 MW y saltos entre 16m y 28m. Para realizar este estudio, se propuso la modelación numérica de la operación de una de estas turbinas, utilizando un software comercial de CFD basado en OpenFOAM (TCAE de la empresa CFDSupport). Como instancia previa, se propuso desarrollar y validar la metodología mediante el modelado numérico de un banco de ensayos de turbinas de bajo salto, con rotores axiales similares a los de las turbinas Kaplan. Este banco, instalado en el IMFIA (Instituto de Mecánica de los Fluidos e Ingeniería Ambiental), permite reproducir de forma controlada fenómenos similares a los que ocurren en la operación a carga parcial de turbinas Kaplan. El objetivo de este trabajo es presentar los principales resultados de dicha etapa de validación, los cuales constituyen un paso fundamental para garantizar la confiabilidad de las simulaciones numéricas a realizar en la turbina Kaplan a escala real bajo condiciones atípicas de operación.