1,721,127 research outputs found
An algorithm for automatic detection of topological changes in water distribution networks
No full textTopological and pressure-driven analyses are an integral part of reliability/risk considerations for a water distribution system. For example, it is often necessary to identify which parts of the dis-tribution network are isolated from water sources after the valves have been closed in response to a mechanical pipe failure. Pressure-driven analysis is then necessary to ascertain the consequences of pipe failures in terms of the performance of the functioning sub-system whilst pipe breaks are being fixed in the isolated area. Therefore, it is extremely useful to have an algorithm for the automatic identification of nodes/pipes disconnected from the water source(s). However, this is a complex problem because valves sometimes significantly modify the network topology. Furthermore, the use of isolation valves can cause a demand shortage to some customers (due to pressure reduction) during the abnormal operating conditions in the system. Thus, pressure-driven simulation of the network behaviour is required. For these reasons a novel algorithm capable of automatic detection of topological network changes is coupled with a robust pressure-driven simulation model. This algorithm is tested on two case studies involving a small artificial water distribution system and a larger, real-life network. The results obtained clearly demonstrate the robustness of the algorithm developed
Extended Period Simulation Analysis Considering Valve Shutdowns
No full textPlanned (e.g. regular maintenance) and unplanned (e.g. pipe burst) interruptions occur regularly in water distribution systems leading to their reduced performance. This paper presents an extended period simulation model capable of assessing system’s performance under these conditions. The extended period simulation model is based on the recently developed steady-state pressure driven hydraulic model and is capable of calculating pressures, flows and hence actual water demands delivered under modified network topology conditions (caused by the use of isolation valves). The model is accompanied by several reliability indicators which can be used to assess system’s performance under interruptions. The above methodology is demonstrated on a real-life case study in Italy. The role of isolation valve design and uncertainty in valve operability is analysed and discussed. The case study results obtained demonstrate that the least cost de-sign/rehabilitation of water distribution systems is likely to result in unreliable systems if the ac-tual network configurations obtained by closing isolation valves in abnormal working conditions are not taken into account
Fast hybrid optmization method for effective pump scheduling
No full textThe cost of electricity used for pumping in water-distribution systems typically represents the largest part of the total operational costs. Therefore, optimization of pump operations is a major concern for water utilities around the world, especially in recent years with significantly increasing energy prices. Recently, to maximize cost and energy savings, pump scheduling is frequently done in real time by integrating the relevant optimization software into the water company’s supervisory control and data acquisition (SCADA) system. This, however, requires solving a complex, large, nonlinear optimization problem in a computationally efficient manner, typically in less than 1 h. To achieve this, the pump-scheduling problem is solved in this paper by a novel hybrid optimization method that uses linear programming (LP) and a greedy algorithm: LPG. The new methodology is applied to two case studies: the artificial, benchmark case study of Anytown network and the real-life pump-scheduling problem of the Richmond water-distribution network (WDN) in the UK. The results obtained clearly demonstrate that the LPG hybrid method is capable of solving real-life pump-scheduling problems in an extremely computationally efficient manner while preserving the accuracy (i.e., the near optimality) of the obtained solution. This makes the method particularly appealing for use in real-time pump-scheduling applications
Detecting topological changes in large water distribution networks
No full textThe issue of detecting topological changes in pipe networks due to failing pipes is an important one, especially when performing reliability analysis of a water distribution system. This manuscript presents an improvement to a recently published algorithm, which used the pseudo-inversion of a system model matrix in order to solve a special linear version of a network simulation model for identifying the disconnected nodes. The new algorithm is based on the Cholesky incomplete factorization of the relevant system matrix. The improved algorithm is capable of automatically identifying nodes/pipes disconnected from the water source(s) in large networks. The algorithm is tested and verified on a case study involving a large network derived from a real-life system. The case study results clearly demonstrate the increased computational efficiency and the robustness of the improved algorithm when compared to the previouslypublished on
Risk based sensor placement methods for burst/leak detection in water distribution systems
Full text linkThis is the author accepted manuscript. The final version is available from IWA Publishing via the DOI in this record.The optimal placement of sensors in water distribution systems for burst/leak detection is usually formulated as an optimization problem. In this study three different risk-based functions are used to drive optimal location of a given number of sensors in water distribution network. A simple function based on likelihood of leak non-detection is compared with two other risk-based functions, where impact and exposure are combined with the leak detection likelihood. The impact is considered proportional to the demand water volume while the exposure is related to the importance of the connections and it is evaluated on social, economic or safety considerations. The methods are applied to a district metered area of the Harrogate network by means of a modified EPANET model, to take into account the pressure driven functioning conditions of the system. The results show that the exposure can lead to a different sensor location ranking with respect to other used criteria and hence the proposed methodology can represent a useful tool for the water system managers to distribute the sensors in the network, complying to hydraulic, social and economical requirements.The authors are grateful for the Erasmus funding which enabled the first author to do most of this work at the University of Exeter in the UK
An effective multi-objective approach to prioritisation of sewer pipe inspection
No full textThe first step in the decision making process for proactive sewer rehabilitation is to assess the condition of conduits. In a risk-based decision context the set of sewers to be inspected first should be identified based on the trade-off between the risk of failures and the cost of inspections. In this paper the most effective inspection works are obtained by solving a multiobjective optimization problem where the total cost of the survey programme and the expected cost of emergency repairs subsequent to blockages and collapses are considered simultaneously. A multi-objective genetic algorithm (MOGA) is used to identify a set of Pareto-optimal inspection programmes. Regardless of the proven effectiveness of the genetic-algorithm approach, the scrutiny of MOGA-based inspection strategies shows that they can differ significantly from each other, even when having comparable costs. A post-processing of MOGA solutions is proposed herein, which allows priority to be assigned to each survey intervention. Results are of practical relevance for decision makers, as they represent the most effective sequence of inspection works to be carried out based on the available funds. The proposed approach is demonstrated on a real large sewer system in the UK
ANALISI SPAZIALE DELLA TEMPERATURA DELL’ACQUA IN RETI DI DISTRIBUZIONE IDRICA E PROPOSTA DI INTERVENTI PER L’ADATTAMENTO AL CAMBIAMENTO CLIMATICO
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