1,721,279 research outputs found
The Identification of Loops in Water Distribution Networks
No full textAbstractThis paper presents an automatic algorithm for the identification of the minimum loops in a multi-source looped water distribution network. This algorithm, obtained as a generalization of that recently proposed by Creaco and Franchini (2014), has the novelty of being able to identify, automatically and in a single run, both the geometric and the fictitious loops of the network. Applications prove that the algorithm has acceptable computation times and can then be profitably adopted in the context of water distribution system analysis
On the choice of the demand and hydraulic modeling approach to WDN real-time simulation
Full text linkThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.This paper aims to analyze two demand modeling approaches, i.e., top-down deterministic (TDA) and bottom-up stochastic (BUA), with particular reference to their impact on the hydraulic modeling of water distribution networks (WDNs). In the applications, the hydraulic modeling is carried out through the extended period simulation (EPS) and unsteady flow modeling (UFM). Taking as benchmark the modeling conditions that are closest to the WDN's real operation (UFM + BUA), the analysis showed that the traditional use of EPS + TDA produces large pressure head and water discharge errors, which can be attenuated only when large temporal steps (up to 1 h in the case study) are used inside EPS. The use of EPS + BUA always yields better results. Indeed, EPS + BUA already gives a good approximation of the WDN's real operation when intermediate temporal steps (larger than 2 min in the case study) are used for the simulation. The trade-off between consistency of results and computational burden makes EPS + BUA the most suitable tool for real-time WDN simulation, while benefitting from data acquired through smart meters for the parameterization of demand generation models
Closure to “Head Reconstruction Method to Balance Flux and Source Terms in Shallow Water Equations” by Enrico Creaco, Alberto Campisano, Alexander Khe, Carlo Modica, and Giovanni Russo
No full textClosure to "peak Demand Assessment and Hydraulic Analysis in WDN Design" by E. Creaco, P. Signori, S. Papiri, and C. Ciaponi
No full textEvaluating water demand shortfalls in segment analysis
No full textIn this paper, two procedures for assessing water demand shortfalls following segment isolation are compared. The first (topological) procedure is based on a simple topological network analysis, and identifies the water demand shortfall as the water demand (under normal operational conditions) relative to the directly and/or indirectly isolated segment(s). The second (hydraulic) procedure is based on a pressure-driven hydraulic simulation of the network after segment isolation. Each of the two procedures was applied to two case studies, and the reliability (expressed in terms of maximum D max and weighted average D¯¯¯¯ water demand shortfall) and economic burden (expressed in terms of number N val or cost C val of installed valves) of the resulting isolation valve system solution were compared. As a whole, the results show that network analysis and redesign are affected by the choice of the global variables (D max or D¯¯¯¯) used to characterize the demand shortfalls in network segments. Analysis of the case studies is followed by a discussion of the rationale behind the choice between the two procedures, which needs to balance accurate demand shortfall characterization with limited computation times, particularly in the multi-objective design stage.E. Creaco, M. Franchini, S. Alvis
Exploring Numerically the Benefits of Water Discharge Prediction for the Remote RTC of WDNs
Full text linkThis paper explores numerically the benefits of water discharge prediction in the real time control (RTC) of water distribution networks (WDNs). An algorithm aimed at controlling the settings of control valves and variable speed pumps, as a function of pressure head signals from remote
nodes in the network, is used. Two variants of the algorithm are considered, based on the measured water discharge in the device at the current time and on the prediction of this variable at the new time, respectively. As a result of the prediction, carried out using a polynomial with coefficients
determined through linear regression, the RTC algorithm attempts to correct the expected deviation of the controlled pressure head from the set point, rather than the currently measured deviation. The applications concerned the numerical simulation of RTC in a WDN, in which the nodal demands are reconstructed stochastically through the bottom-up approach. The results prove that RTC benefits from the implementation of the prediction, in terms of the closeness of the controlled variable to the set point and of total variations of the device setting. The benefits are more evident when the water discharge features contained random fluctuations and large hourly variations
Scaling models of intensity–duration–frequency (IDF) curves based on adjusted design event durations
No full textThis paper deals with intensity–duration–frequency (IDF) curves, which express the relationship between average rainfall intensity and event duration for various probabilities of non-exceedance (or return periods) for the design/analysis of hydraulic interventions and infrastructures in riverine and urban drainage contexts. New scaling models are proposed to develop a single IDF model valid for all durations, from below 1 h to 24 h. In these models, the scale invariance is applied to rainfall intensity to obtain a parsimonious IDF structure capable of defining a family of IDF curves at various return periods. The main novelty consists of the formulation of simple and multiple scale invariance based on adjusted design event durations. The parameterization is carried out in two phases: in the first phase, the adjustment size is searched for iteratively while the other parameters of the IDF structure are directly obtained in cascade; in the second phase, which enables considering different reliability levels for extreme rainfall data as a function of sample length at different durations, parameter refinement is carried out by means of a local optimization algorithm. The second step accommodates data samples of different extension as a function of available data at different durations. The application to four case studies at various latitudes in Europe, namely Helsinborg (Sweden), Frauenwald (Germany), Pavia and Erice (Italy), proves the IDF structure to fit well the quantile predictions of extreme rainfall data for specified durations below and above one hour
Low Level Hybrid Procedure for the Multi-objective Design of Water Distribution Networks
No full textAbstractThis paper presents a procedure for the multi-objective design of looped water distribution systems. The main block of the procedure encompasses four sub-algorithms. Since one sub-algorithm co-ordinates the others (which then operate in a subordinate way), the procedure can be inserted into the category of low level hybrid procedures. The results of the algorithm are optimal solutions in the cost-reliability space, with reliability being compactly expressed through the network resilience metric. The application to four case studies shows the benefits of the new algorithm in terms of numerical and computational efficiency with respect to a multi-objective genetic algorithm
Economic analysis of pressure control for leakage and pipe burst reduction
No full textThis paper presents an economic analysis of pressure control solutions for leakage and pipe burst reduction. In detail, it explores the operating conditions under which the installation of conventional mechanical pressure reducing valves (PRVs) or remotely real-time controlled (RTC) valves are cost effective compared to a scenario with no control. For a range of system sizes, hydraulic extended period simulations and empirical formulas were used to estimate leakage rates and pipe bursts, respectively, in numerous operational scenarios, including different precontrol leakage levels and demand patterns, the absence of pressure control, and the installation of a PRVor RTC valve. The total cost of the controlled system, including the installation cost of the control device, the flow-dependent operation and maintenance (O&M) cost, and the pipe burst repair cost over the planning horizon, was compared with the water-related O&M and pipe burst repair costs of the uncontrolled system. The results pointed out that no pressure controls are needed if leakage and the variable O&M cost of water are low. When these variables are high, remote RTC is attractive, especially when the demand pattern is peaked and the system is large. For more moderate cost and leakage, a conventional PRV may be better than RTC, especially in small systems and for relatively smooth demand patterns
Comparison of algorithms for the optimal location of control valves for leakage reduction in WDNs
Full text linkThe paper presents the comparison of two different algorithms for the optimal location of control valves for leakage reduction in water distribution networks (WDNs). The former is based on the sequential addition (SA) of control valves. At the generic step Nval of SA, the search for the optimal combination of Nval valves is carried out, while containing the optimal combination of Nval - 1 valves found at the previous step. Therefore, only one new valve location is searched for at each step of SA, among all the remaining available locations. The latter algorithm consists of a multi-objective genetic algorithm (GA), in which valve locations are encoded inside individual genes. For the sake of consistency, the same embedded algorithm, based on iterated linear programming (LP), was used inside SA and GA, to search for the optimal valve settings at various time slots in the day. The results of applications to two WDNs show that SA and GA yield identical results for small values of Nval. When this number grows, the limitations of SA, related to its reduced exploration of the research space, emerge. In fact, for higher values of Nval, SA tends to produce less beneficial valve locations in terms of leakage abatement. However, the smaller computation time of SA may make this algorithm preferable in the case of large WDNs, for which the application of GA would be overly burdensome
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