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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]

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]