aqualibrium competition laboratory data and epanet simulations

Abstract The Aqualibrium competition [1] is a fun way to learn about water supply and distribution. A pipe network has to be built with the aim of equally distributing a given volume of water between three reservoirs. The rules of such a competition prescribe that a looped network has to be built and this makes the problem quite complex because of the well-known non-linearity of the governing equations. EPAnet is a powerful tool to improve and fasten the solution of the problem. At the Water Engineering Laboratory (WEL) of the University of Perugia an Aqualibrium equipment is used within the Civil Engineering courses. EPAnet was used to simulate the behaviour of the Aqualibrium network, but the results showed some discrepancies between laboratory tests and numerical simulations under some flow conditions. These discrepancies, as well as the critical role played by energy dissipation mechanism, are discussed in this paper

Modeling the Effects of Distribution System Topology on Water Quality

Inadequate treatment of drinking water causes the formation of disinfection by-products and the regrowth of harmful microbial species. Various studies have addressed the problem of water quality monitoring, but very few have employed topological analysis, a valuable mathematical tool widely applied in biological, business, and social research. This thesis examines the relationship between the topological properties of water distribution systems and water-quality models. In particular, the research proposes a novel framework for mapping network topological attributes to water-quality models. This research adopts topological metrics to assess the accuracy of the predictions of chlorine concentrations in dead ends. It examines four fundamental water-quality models: advection, advection-dispersion, bulk-advection, and bulk-advection-dispersion. The results show the bulk-advection-dispersion model has larger root mean square errors in networks with a grid structure, and that topological metrics are generally correlated with water-quality models, although more studies are required to develop this correlation in detail

Extending the global gradient algorithm to unsteady flow extended period simulations of water distribution systems

This paper introduces an extension of the Global Gradient Algorithm (GGA) to directly solve unsteady flow problems arising from the presence of variable head water storage devices, such as tanks, in Extended Period Simulations (EPS) of looped water distribution networks (WDN). Such a modification of the original algorithm was motivated by the need to overcome oscillations and instabilities reported by several users of EPANET, a worldwide available package, which uses the GGA to solve the looped WDN equations. The set of partial differential equations describing the time and space behaviour of a water distribution system is here presented. It is shown how an unsteady flow GGA can be derived by simple modifications of the original steady-state GGA. The performances of the new algorithm, referred to as EPS-GGA, are compared with the results provided by EPANET on an extremely simplified example, the solution of which is qualitatively known. As opposed to EPANET which shows significant instabilities, the EPS-GGA is stable under a wide variety of increasing integration time intervals

Dependent infrastructure system modeling: A case study of the St. Kitts power and water distribution systems

Critical infrastructure systems underlie the economy, national security, and health of modern society. These infrastructures have become increasingly dependent on each other, which poses challenges when modeling these systems. Although a number of methods have been developed for this problem, few case studies that model real-world dependent infrastructures have been conducted. In this paper, we aim to provide another example of such a case study by modeling a real-world water distribution system dependent on a power system. Unlike in the limited previous case studies, our case study is in a developing nation context. This makes the availability of data about the infrastructure systems in this case study very limited, which is a common characteristic of real-world studies in many settings. Thus, a main contribution of the paper is to show how one can still develop representative, useful models for systems in the context of limited data. To demonstrate the utility of these types of models, two examples of different analyses are performed, where the results provide information about the most vulnerable parts of the infrastructures and critical linkages between the power and water distribution systems.publishedVersio

Disinfection by products estimation in a water distribution network

Even though disinfection is necessary to ensure water safety for human consumption, some disinfectants produce disinfection by-products (DBPs) that may be dangerous for human health. Current European legislation obligates water distributors to limit some DBPs concentration to final consumers. Then, water companies must control these compounds and are obligated to periodically monitor their network. DBPs modeling can be very useful for estimating online DBPs concentration throughout the network, increasing DBPs control and knowledge, but avoiding DBPs analytics time and resources consumption [1]. Trihalomethanes (THM), the first DBPs discovered, have long been the most studied and modeled. Previous studies have mostly used linear relations between variables and THM concentration, but also computational modelling, mechanistic and data driven models [2, 3]. Even though, there are still challenges to beat: most studies use a small database and laboratory-scale for model building, forgetting the impact of network pipelines and season. In addition, significant variables for DBPs’ formation such as retention time are most of the time neglected due to its difficulty to measure. Finally, THMs are not the only DBPs generated from disinfection or even the most toxic: other DBPs must be studied, and their formation pathways along the network investigated. In this study, data from a full-scale distribution network was used: online sensors and sampling campaigns. To include hydraulic conditions as retention time, EPANET software and R programming are used to simulate the network. Different models, mechanistic and data driven, have been used to estimate the chlorine decay and DBP formation within the network. Results of the calibration and validation of these models and the conclusions obtained are presented.Peer ReviewedPostprint (published version

Parallel Computing in Water Network Analysis and Leakage Minimization

[EN] In this paper a parallel computing based software demonstrator for the simulation and leakage minimization of water networks is presented. This demonstrator, based on the EPANET package, tackles three different types of problems making use of parallel computing. First, the solution of the hydraulic problem is treated by means of the gradient method. The key point in the parallelization of the method is the solution of the underlying linear systems, which is carried out by means of a multifrontal Choleski method. Second, the water quality simulation problem is approached by using the discrete volume element method. The application of parallel computing is based on dividing the water network in several parts using the multilevel recursive bisection graph partitioning algorithm. Finally, the problem of leakage minimization using pressure reducing valves is approached. This results in the formulation of an optimization problem for each time step, which is solved by means of sequential quadratic programming. Because these subproblems are independent of each other, they can be solved in parallel.The writers wish to acknowledge the financial support provided by the ESPRIT program of the European Commission (HIPERWATER, ESPRIT project 24003), by the CICYT TIC96-1062-C03-01 project, and also by research staff training grants from the Spanish government and the autonomous government of the Comunidad Valenciana in Spain.Alonso Ábalos, JM.; Alvarruiz Bermejo, F.; Guerrero López, D.; Hernández García, V.; Ruiz Martínez, PA.; Vidal Maciá, AM.; Martínez Alzamora, F.... (2000). Parallel Computing in Water Network Analysis and Leakage Minimization. Journal of Water Resources Planning and Management. 126(4):251-260. https://doi.org/10.1061/(ASCE)0733-9496(2000)126:4(251)S251260126

Integrated System for Hydraulic Simulations

The work described in this paper is aimed at applying and co-operating of modern information technologies and mathematical modeling to make a risk analysis of the water-supply in big cities. It is instrumental in the investigation of the hydraulics of water-supply systems using the simulation model EPANET executed on the underlying high-performance computing infrastructure. The simulation process is integrated with the GIS environment in order to correct input data and visualize the simulation output. Input data for the model can be modified directly within the designed scientific gateway which enables hydraulic domain experts to interact comfortably with the HPC capacity. Furthermore, the system includes some data mining capabilities forming bridges between the hydraulic data storage and available hydrological measurements focused on water consumption modeling and predictions. In simulating the main emphasis is given to optimize the measure of a similarity between the mathematical model and the real system in order to obtain reliable results

An efficient null space inexact Newton method for hydraulic simulation of water distribution networks

Null space Newton algorithms are efficient in solving the nonlinear equations arising in hydraulic analysis of water distribution networks. In this article, we propose and evaluate an inexact Newton method that relies on partial updates of the network pipes' frictional headloss computations to solve the linear systems more efficiently and with numerical reliability. The update set parameters are studied to propose appropriate values. Different null space basis generation schemes are analysed to choose methods for sparse and well-conditioned null space bases resulting in a smaller update set. The Newton steps are computed in the null space by solving sparse, symmetric positive definite systems with sparse Cholesky factorizations. By using the constant structure of the null space system matrices, a single symbolic factorization in the Cholesky decomposition is used multiple times, reducing the computational cost of linear solves. The algorithms and analyses are validated using medium to large-scale water network models.Comment: 15 pages, 9 figures, Preprint extension of Abraham and Stoianov, 2015 (https://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0001089), September 2015. Includes extended exposition, additional case studies and new simulations and analysi