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The pipe component of a water distribution network (WDN) is sized based on the fixed design demand considering a peak factor and design period. Simulation of the designed network by a hydraulic solver provides nodal pressure head, head loss, velocity, and flow in each pipe as the prime outputs for the design demand, and it can also be used for extended-period simulation for a particular demand pattern over the supply hours. But, in reality, the behavior of the network does not match with such a result in an intermittent water supply (IWS) system due to the fact that all house service connections behave as an uncontrolled orifice. This has made it a challenging task in understanding and in predicting the behavior of the networks by the municipal engineer once the water starts flowing through the house service connections (HSCs). Though the municipal engineer provides the same pipe size for HSCs to all residences, the flow received by each house could vary based on the available pressure head at the ferrule point of the main water supply pipeline. In reality, maintaining constant pressure at each HSC is not feasible due to frictional head loss. Hence, variation in flow at the HSC is inevitable even with a small water supply system. This paper illustrates how to simulate the behavior of an IWS system based on the number of HSCs provided to each pipeline using a hydraulic solver. Hydraulic simulation of the water distribution network that provides IWS to consumers can be implemented easily by adding a fictitious node by assigning an appropriate emitter coefficient to each demand node through a fictitious link having a check valve in it. The method for finding the appropriate value of the emitter coefficient that helps in simulating HSCs is illustrated in the present work. [ABSTRACT FROM AUTHOR]

The range of pipe roughness values in both cases (triangular and trapezoidal) at the 0 HT ht level is the same, i.e., 110 to 130. For example, the minimum and maximum values obtained by the authors for HT ht are 8.88 and HT ht , while Sivakumar et al. ([5]) reported 5.81 and HT ht . Because the range of pipe roughness values at the 0 HT ht level in both triangular and trapezoidal cases is the same, MFs of pipe discharges and nodal heads at the 0 HT ht level should be identical. However, for other HT ht levels, these are different. [Extracted from the article]

This document is a closure to a previous paper titled "Analysis of Intermittent Water Distribution Networks Using a Dummy Emitter Device at Each Demand Node." The closure addresses comments and criticisms made by discussers regarding the original paper. It explains the methodology used to analyze intermittent water supply (IWS) and highlights the differences in results obtained by different models. The closure also discusses the applicability of the emitter approach in various scenarios and suggests modifications for specific cases. Overall, the closure provides insights into the analysis of IWS systems and the factors that can affect their performance. [Extracted from the article]

A similar analysis is not applicable for Case Study 2 because the settings of the HT ht values are 0 for both PSVs and emitters. Hence, the discussers used PSV settings of zero instead of the HT ht values given in Table 2 of the original paper. The probable reason behind the authors' incorrect results for HT ht and 1.5 is that the default value of 0.5 might have been used for the global emitter exponent. [Extracted from the article]

EPANET 2 software has been widely used among researchers and practitioners from its inception for hydraulic analysis. This technical note presents a method to simulate pressure-dependent volume-based demands in a single extended-period simulation run of EPANET 2. In the proposed method, artificial strings made up of a pipe with a minor loss, pressure-sustaining valve, pipe of negligible resistance, and tank are added to the demand nodes before running the hydraulic analysis. The time required to satisfy a volume-based demand is determined as the time required to fill the artificial tank connected to the demand node for normal and pressure-deficient conditions. All the simulations were carried out using the available functions of the graphical user interface of EPANET 2. The proposed method was applied to a two-source looped network available from the literature and additionally compared with an existing method available in the literature using two example networks. [ABSTRACT FROM AUTHOR]

A new approach is presented for the optimization of steel lattice towers by combining genetic algorithms and an object-oriented approach. The purpose of this approach is to eliminate the difficulties in the handling of large size problems such as lattice towers. Improved search and rapid convergence are obtained by considering the lattice tower as a set of small objects and combining these objects into a system. This is possible with serial cantilever structures such as lattice towers. A tower consists of panel objects, which can be classified as separate objects, as they possess an independent property as well as inherent properties. This can considerably reduce the design space of the problem and enhance the result. An optimization approach for the steel lattice tower problem using objects and genetic algorithms is presented here. The paper also describes the algorithm with practical design considerations used for this approach. To demonstrate the approach, a typical tower configuration with practical constraints has been considered for discrete optimization with the new approach and compared with the results of a normal approach in which the full tower is considered. [ABSTRACT FROM AUTHOR]

It is shown that the quasi-steady-state approach to water-distribution-system simulation, which is adopted in most of the currently available hydraulic simulators, may result in nonunique solutions (in terms of nodal pressures) in the practically occurring case of a network section fed through a flow control valve whose setting is equal to the sum of the required demands in the section (this being true both for demand-driven and pressure-driven analyses). This paper presents an algorithm that allows one to determine whether nonunique solutions occur and, if so, to determine the nodal pressure range in which they lie. The algorithm is illustrated by the example of an operating city water distribution network. [ABSTRACT FROM AUTHOR]

This document provides a summary of a paper titled "Head-Drop Method for the Modeling of Pressure Reducing Valves and Variable Speed Pumps in Water Distribution Networks." The paper introduces the head-drop method for water distribution networks with pressure-regulating devices and presents an algorithm for pressure reducing valves (PRVs). The authors also extend the method to pressure-sustaining valves (PSVs) and implement it in the global gradient algorithm. The document discusses the results of a simulation comparing the head-drop method with a hybrid simulator, highlighting the importance of using criteria 1 and 2 together and setting the head drop for open valves to zero. [Extracted from the article]

As shown by the examples given in this paper, a commonly used, commercially available water distribution network modeling software may produce unrealistic results for flow control valves (FCVs) with a nonzero loss coefficient. This paper presents and discusses a simple technique to remedy this problem. According to this technique, an FCV with a nonzero loss coefficient K is modeled as a composite link that consists of an FCVof the same setting with a zero loss coefficient and an artificial pipe of negligibly small major loss with a diameter equal to the FCV diameter and a minor loss coefficient equal to K. The proposed technique can be implemented using the discussed software without any modification of its hydraulic solver. [ABSTRACT FROM AUTHOR]

The article comments on hydraulic simulation techniques for water distribution networks to treat pressure deficient conditions. Further discusses about considering demand-driven analysis (DDA) and pressure-driven analysis (PDA); and also mentions about involving all nodes with a computed negative pressure irrespective of whether a total head reverse will occur or not after the pressure at those nodes is put equal to zero.

Consider a PRV placed in pipe HT ht to control the pressure at its downstream node. [Extracted from the article]

The following corrections should be made to the original paper: Step 3 in the "Methodology" section should read: 3. Run the GGA until the sum of all link flow and emitter outflow changes divided by the sum of all link flows and emitter outflows is less than a specified stopping tolerance HT ht . [Extracted from the article]

This technical note presents a hybrid simulator designed for water distribution networks with control valves. The simulator is a modification of EPANET 2 that can handle valves using both the EPANET 2 heuristics and a recently proposed alternative method that models valves as pipes whose resistance is adjusted to meet the valve setting. The method copes with cases where the EPANET 2 heuristics fails, but it requires a larger number of iterations. The hybrid simulator starts with running the EPANET 2 heuristics and switches to the alternative method only if the former fails (cannot find a solution or produces incorrect results), thus using to advantage the fast convergence of the EPANET 2 heuristics and the more stable yet slower convergence of the alternative method. Verification tests demonstrated the ability of the hybrid simulator to deal with ill-posed problems and large networks with thousands of nodes, pipes, and valves. [ABSTRACT FROM AUTHOR]

This paper presents a simple valve simulation method integrable into the global gradient algorithm (GGA), which is widely used in hydraulic analysis of water distribution systems. In the proposed method, valves are treated as pipes whose resistance is adjusted in the course of the GGA iteration to meet the valve setting. This method features a unified approach to pressure control and flow control valves. Comparison tests on example networks have shown that the proposed method computes the same results as an independent optimization-based method in a comparable number of iterations and copes with the cases where EPANET 2 produces incorrect results. The proposed method may easily be integrated into existing GGA-based hydraulic solvers, in particular into that of EPANET 2. [ABSTRACT FROM AUTHOR]