1,721,099 research outputs found
Prioritizing pipe replacement: From multiobjective genetic algorithms to operational decision support
No full textDeterioration of water distribution systems and the optimal allocation of limited funds for their rehabilitation represent crucial challenges for water utility managers. Decision makers should be provided with a set of “informed” solutions to select the best rehabilitation plan with regard to available resources and management strategies. In a risk-based scenario, such an approach should result in an element-wise prioritization scheme based on individual pipe rehabilitation/replacement effectiveness. This manuscript describes a framework for devising a short-term decision support tool for pipe replacement. The approach allows for the introduction of economic, technical, and management rationales as separate objectives to produce a pipe-wise prioritization scheme which is achieved by ranking pipes selected during a multiobjective (MO) evolutionary optimization of replacement scenarios. Such a procedure helps overcome the doubts in choosing among the solutions obtained by MO evolutionary optimization due to the diverse sets of pipes selected for replacement even when they are economically comparable. The effectiveness of the entire framework is demonstrated on a real U.K. water distribution system
More realistic water distribution network design using pressure-driven demand and leakage
No full textThe traditional optimization paradigm used in system design focuses on network cost minimization and the maintenance of nodal pressures by relying on a demand-driven simulation of the network. This article describes a more realistic optimal design approach in which simulations are conducted with a pressure-driven model in order to assess unsupplied network demand and actual leakage flow rates. Reliability, within the context of unsatisfied demand and leakage, serves as an additional objective criterion in the optimization formulation. The assumption of a maximum network deterioration level is revisited and shown to be useful for improving reliability in the face of escalating leakage
Calibration of Design Models for Leakage Management of Water Distribution Networks
Full text linkWater losses in urban water distribution networks (WDN) accelerate the deterioration of such infrastructures. The enhanced hydraulic modelling provides a phenomenological representation of WDN hydraulics, including the modelling of leakages as function of pipe average pressure and deterioration. The methodological use of such models on real WDN was demonstrated to support the planning of leakage management actions. Nonetheless, many water utilities are still in the process of designing flow/pressure monitoring, thus data available are not enough to perform detailed calibration of such models. This work presents a physically based approach for the calibration of WDN hydraulic models aimed at supporting leakage management plans since early stages. The proposed procedure leverages the key role of mass balance in enhanced hydraulic models and the technical insight on pipe deterioration mechanisms for various quantity and quality of available data. Two calibration studies of real WDNs demonstrate the feasibility of the approach and show that the distribution of leakages in the WDN does not much influence the pressure values, which confirms the need for flow measurements at monitoring districts for leakage and asset management
An overview of water demand: Volume vs. Pressure based demands
No full textWhile there is no question about the fact that demands in a water distribution system can be dependent on pressure, the importance of considering pressure based demands in modeling has been widely discussed. This discussion often centres on whether demands are pressure or volume based. This, however, is the wrong question. Demands are BOTH pressure and volume based and demands are really a sum of several difference components of demand including volume based demand, controlled pressure based demand, uncontrolled pressure based demand and leakage. Each of these components is described in the paper with some special consideration of the case where pressure approaches zero and the implications of considering these components
Advances in Data-Driven Analyses and Modelling Using EPR-MOGA
No full textEvolutionary Polynomial Regression (EPR) is a recently developed hybrid regression method that combines the best features of conventional numerical regression techniques with the genetic programming/symbolic regression technique. The original version of EPR works with formulae based on true or pseudo-polynomial expressions using a single-objective genetic algorithm. Therefore, to obtain a set of formulae with a variable number of pseudo-polynomial coefficients, the sequential search is performed in the formulae space. This article presents an improved EPR strategy that uses a multi-objective genetic algorithm instead. We demonstrate that multi-objective approach is a more feasible instrument for data analysis and model selection. Moreover, we show that EPR can also allow for simple uncertainty analysis (since it returns polynomial structures that are linear with respect to the estimated coefficients). The methodology is tested and the results are reported in a case study relating groundwater level predictions to total month-ly rainfall
Supporting decision on energy vs. asset cost optimization in drinking water distribution networks
Full text linkOne of the challenges for water utilities is the optimal asset design ( i. e. maximum power of pump systems, tank volumes and pipe diameters) of water distribution networks (WDN) while optimizing operational efficiency ( i. e. energy consumption and cost). Besides the classical minimization of capital cost while providing sufficient supply service, the operational sustainability is an emerging issue. As the reduction of each component of capital and energy costs are conflicting with each other, the optimization problem is multi-objective. This work presents the study of the robustness of solutions of the Pareto set as a further element to support the decision
Advancements in water distribution network simulation by Enhanced GGA
No full textThe advent of information technology and geographical information systems in water industry allows a detailed description of Water Distribution Network (WDN) topology and its boundary conditions. However, the complexity of network analysis and the mathematical problem size related to the hydraulic simulation considerably increase, especially for large WDN. The present paper introduces a network simplification strategy based on a correction paradigm adopted by Giustolisi and Todini in the Enhanced Global Gradient Algorithm (EGGA). Starting from the original topology of the analyzed WDN, the proposed strategy identifies the serial nodes/sections (i.e. those adjacent to two nodes/pipes only) which are iteratively removed from network topological representation. Therefore, the new network topology contains only those nodes joining three or more pipes or the terminal nodes of branched sections. Such a topological simplification results into a lower dimension of the topological matrices underlying the hydraulic simulation model. This way the WDN analysis can be performed using the EGGA formulation increasing computational efficiency, especially for large-size networks, without forfeiting energy and mass balances of the original hydraulic system. The paper reports the general formulation of EGGA and the strategy is tested on two large-size networks (of 1,461 and 12,513 internal nodes). The results are compared with those obtained using the original WDN topology and the classic Global Gradient Algorithm (GGA). Thus, it has been demonstrated that the EGGA strategy of simplification allows achieving a computational efficiency while correctly representing the hydraulic behaviour of the network
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