Pressure-driven Analysis Research Articles

Optimal Design of Intermittent Water Distribution Network Considering Network Resilience and Equity in Water Supply

In urban areas of developing countries, due to industrialization and population growth, water demand has been increasing significantly, thereby increasing stress on the existing water distribution systems (WDSs). Under these circumstances, maintaining equity in the allocation of water becomes a significant challenge. When building an intermittent water distribution system, it is important to provide a minimum level of supply that is acceptable as well as water supply equity. A non-dominated sorting genetic algorithm (NSGA-II) is employed for the optimal design of an intermittent water distribution network (WDN). Network resilience is taken as a measure of reliability (In), while the uniformity coefficient (CU) is taken as a measure of equity in the water supply. Maximizing network resilience, uniformity coefficient, and minimization of cost of the network are considered as the objectives in the multi-objective optimization model. Pressure-driven analysis (PDA) is used for the hydraulic simulation of the network. The NSGA-II model is applied and demonstrated over two water distribution networks taken from the literature. The results indicate that reliability and equity in WDNs can be accomplished to a reasonable extent with minimal cost.

An assessment of the artificial modelling elements approach to the pressure-driven analysis of water distribution networks

Abstract EPANET 2.2 is a newly introduced upgraded version of EPANET 2 that can be used for both pressure-driven analysis (PDA) and demand-driven analysis (DDA) of water distribution networks. Moreover, it has certain limitations concerning the minimum and required pressure head parameters used for PDA, which leads to inaccurate simulation results. Another limitation of the PDA option of EPANET 2.2 is its inability to simultaneously consider pressure-dependent demands with pressure-independent fire demands. In this article, the reason for the spurious convergence is identified, and it is shown that the spurious convergence of EPANET 2.2 can be addressed by extending the energy balance convergence criterion to include the virtual demand links employed in the EPANET 2.2 formulation of PDA. On the other hand, interest in the methods that use artificial modelling elements in EPANET 2 for PDA is increasing rapidly. The implementation of the method presented in this paper (termed the alternative PDA approach) allows an extended period simulation of large networks with complex demand patterns, multiple tanks, reservoirs, pumps, valves, and thousands of pipes. Two benchmark networks and two real-world networks were analysed by both the alternative PDA approach and EPANET 2.2 and the results were compared.

A complete digital water experience to support real leakage management planning

In the next years digital transition of Water Distribution Networks (WDNs) will represent a long-standing challenge for triggering innovations in the WDNs management tasks. The ongoing impulse for innovation, boosted also by the economic resources for post-pandemic recovery, is opening novel opportunities for technicians and researchers in the context of Digital Water. This work reports the key steps where novel concepts and tools of Digital Water have been used to support consultant companies in designing WDN leakage management actions in a real WDN managed by Acquedotto Pugliese, in Southern Italy. The Digital Water Services (DWSs) were used to support key phases of the workflow, including validation of topological data and integration of georeferenced connection to private properties; calibration of advanced hydraulic model exploiting mass-balance in pressure-driven analysis; the application of strategies for DMA design and pressure control; and the planning of pipe rehabilitation. WDNetXL platform was used to develop WDN Digital Twin and exploit the DWSs. Applying the Digital Water experience to multiple WDNs managed by the same provider also enabled planning the best courses of actions accounting for investments vs. expected leakage reduction at global scale.

Pressure Driven analysis of water distribution systems for preventing siphonic flow

The analysis of the water distribution network is complicated and requires several assumptions to simplify its problem definition. Demand Driven Analysis (DDA) is typically used to analyse the network assuming that all network nodes can deliver the required demand regardless of the available pressure. In the case of analysing an existing network under deficit condition such as pipe breakage or extra demand required for firefighting, assumptions used to simulate the network with DDA is not valid. Node Head Flow Relationship (NHFR) should be considered through Pressure Driven Analysis (PDA) to analyse the network. Most PDA methods assume that the networks are airtight which means that if the pressure at any demand node is negative, delivered demand will be equal to zero and the flow is permitted in the connected pipes (Siphonic flow). This assumption is hydraulically incorrect since the air is allowed to get into the connected pipes and prevent their flow leading to node isolation. In this paper, a new Pressure Driven Analysis to Prevent Siphonic Flow (PDA-SF) approach is proposed to analyze the network under deficit conditions and consider isolating the nodes that show available head less than node elevation. The PDA-SF was tested and compared to previous methods in four case studies under steady state analysis or extended period simulation. The case studies cover also different network conditions whether node isolation is needed or not. The PDA-SF was able to solve different networks where other methods failed to achieve the required demand or service pressure. The new PDA-SF method shall enable peers and modelers to better simulate and analysis water distribution networks.

Graphical user interface for water distribution network pressure-driven analysis using artificial elements

Graphical user interface for water distribution network pressure-driven analysis using artificial elements

Strategy to Enhance Emergency Interconnected Operation of Water Distribution System

This study identified the causes of insufficient emergency interconnected operation (EIO) performance, such as pressure-related problems and connection problems caused by elevation differences between blocks, the characteristics and locations of emergency interconnection pipes (EIPs), and pumps. Then, it tested four strategies to improve the EIO performance, including increasing the EIP diameter or installing additional EIPs, pressure reducing valves (PRVs), or pumps. The advanced pressure-driven analysis model was applied to quantify the EIO performance improvement achieved using these strategies. Further, these strategies were tested in a real water distribution system. To solve the low-pressure problem, the EIP diameter was increased and an additional pump was installed; the former did not significantly improve, whereas the latter improved supply by 20–30%. To solve the high-pressure problem, PRVs were installed to maintain the EIO performance effectively. To solve connection problems, new EIPs were installed. Although this improved the supply performance, the installation of pumps was recommended to overcome elevation differences. The proposed strategies should contribute to the allocation of facilities such as EIPs, pumps, and PRVs for realizing effective EIO.

Dynamic segment criticality analysis: A precursor to scheduling of maintenance routines in water distribution networks

This study proposes a framework for dynamic segment criticality analysis and its implications on scheduling of some reactive maintenance routines in water distribution networks (WDNs). The framework harmonises multilayer networks which are capable of ascertaining the dynamics of WDNs in discrete time and a novel hybrid segment criticality measure (SCM) to achieve dynamic segment criticality analysis. The novel hybrid SCM utilises reachability theory from complex networks, which accounts for multiple sources, cyclic paths in WDNs, and demand shortfall attributed to segment isolation is computed using Pressure Driven Analysis (PDA) courtesy EPANET. Using a benchmark WDN, North Marin Water District Network, as a case study we have demonstrated the efficacy of the proposed framework and its ability to capture the dynamics of WDNs and evaluate the criticality of any segment given any temporal window. The results indicate the framework accurately evaluates the criticality of all segments within any temporal window and establishes the fact that segment criticality varies with time. Based on the results of this study reactive maintenance routines could be scheduled during temporal periods where the segment criticality measure is minimal to avoid excessive service disruption and customer displeasure. This study supports managers of water utilities with a decision support system to accurately schedule maintenance routines and evaluate segment criticality.

Comparing alternative PDA solvers with EPANET

Abstract This work compares several alternative methods of pressure-driven analysis (PDA) implemented within the code base of the EPANET water distribution system modeling software. The resulting code includes a direct method, the original and a newly modified version of the inverse method currently used by EPANET 2.2, and two recently published methods (the global gradient approach-based PDA and the active set method). The latter four methods solve PDA problems using an inverse flow–pressure relationship, whereas the direct method uses the original relationship. The alternative methods were extensively tested, and their performance was compared over several case study water distribution networks of vastly different sizes and complexities. The results showed that all of the new inverse methods are equally efficient and reliable, whereas the direct method is less reliable by having a higher frequency of failing to converge.

Erratum for “Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves” by Nikolai B. Gorev, Vyacheslav N. Gorev, Inna F. Kodzhespirova, Igor A. Shedlovsky, and P. Sivakumar

Erratum for “Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves” by Nikolai B. Gorev, Vyacheslav N. Gorev, Inna F. Kodzhespirova, Igor A. Shedlovsky, and P. Sivakumar

Evaluation of service pressure regulation strategy on the performance of a rural water network based on pulse demand; using the method of characteristics

Abstract Reducing the occurrence of pipe bursts, reducing leakage, and reducing energy consumption are the three main goals in implementing pressure control programs in water distribution networks. Service pressure regulation strategy is an evolved approach that encompasses all goals of pressure management. This paper has investigated this approach in a rural network with hydraulic complexities as a case study so that some parts of the network have excess pressure and other low pressure. A computer code based on the method of characteristics (MOC) has been developed for network hydraulic analysis. The generated code analyzes unsteady flow, pressure-driven demand analysis, and dynamic adjustment of pressure control valves based on the target node. Also, the experimental results of a laboratory network have been applied to validate and calibrate the numerical simulation. In addition, by measuring the flow rate and pressure of the network and the results of the minimum night flow method, three consumption patterns were used to generate pulsed nodal demands. Studies show that creating pressure-management areas by hydraulic analysis by MOC will determine the best control strategies. The mean pressure decreased 54% by applying this strategy. Furthermore, the average fluctuations of pressure reduced from 9.7 meters to 3.5 meters.

Qualification of Hydraulic Analysis Models for Optimal Design of Water Distribution Systems

The hydraulic analysis of water distribution systems (WDSs) is divided into two approaches, namely, a demand-driven analysis (DDA) and a pressure-driven analysis (PDA). In DDA, the basic assumption is that the nodal demand is fully supplied irrespective of the nodal pressure, which is mainly suitable for normal operating conditions. However, in abnormal conditions, such as pipe failures or unexpected increases in demand, the DDA approach may cause unrealistic results, such as negative pressure. However, despite these realistic hydraulic analysis approaches for WDSs being emphasized in the design process, this consideration was lacking in the design aspect. Therefore, in this study, the designs by the DDA-based design model and PDA-based design model are compared, and their design characteristics are analyzed to identify the efficiency of the WDSs design under abnormal system conditions. The developed PDA model was applied to three networks (a well-known benchmark system and a real-life WDN), and the results showed that the proposed model is superior to other reported models when dealing with negative pressure under abnormal conditions. In addition, the optimal design of WDN considered PDA is presented, and the optimal construction cost is decreased to increase the percentage of PDA.

Application of Parameter-Less Rao Algorithm in Optimization of Water Distribution Networks Through Pressure-Driven Analysis

Application of Parameter-Less Rao Algorithm in Optimization of Water Distribution Networks Through Pressure-Driven Analysis

Pressure Flow–Based Algorithms for Pressure-Driven Analysis of Water Distribution Networks

In recent years, pressure-driven analyses of water distribution systems using pressure-flow relationships (PFRs) were shown to be more computationally efficient than those based on flow-pressure relationships (FPRs), such as the widely used Wagner equation and various spline approximations. Using a PFR enhances the convergence properties of the Newton–Raphson method used by most water distribution network (WDN) solvers. This paper derives a new way of incorporating a PFR into the classical Todini and Pilati global gradient algorithm (GGA). The convergence properties of the resulting solution algorithm are compared with those from two other existing PFR algorithms, EPANET 2.2 and the active-set method (ASM), as well as from a conventional flow-pressure–based algorithm on a number of different networks of varying size.

Improvement Methods for Supply Performance in Emergency Interconnection Plans

When operating a water supply network (WSN), pipe failures and water service interruptions are inevitable. A large-scale water service interruption decreases the reliability of a WSN; therefore, an emergency interconnection plan (EIP) is adopted to prevent it. To establish an EIP involving emergency interconnection pipes, in most cases, only the operation plan is considered. However, it is required to evaluate possible interconnected supply areas (PISAs) from the EIP to achieve the purpose of the EIP. It is obvious that PISA is dependent on the structure of the WSN, elevation difference between the adjacent interconnected blocks, size and location of the emergency interconnection pipes, and inline pumping station. In this study, we categorized the reasons resulting in insufficient PISA from the EIP and suggested improvement methods such as increasing the pipe diameter, new pumping stations, adding emergency interconnection pipes, and adding pressure relief valves. To quantify the effect of the improvement methods on the performance of the EIP, we applied them to a real WSN and estimated the emergency supply rate for each improvement method by using Pressure Driven Analysis (PDA) was used as the hydraulic simulation tool. Consequently, each improvement method increased the PISA and the emergency supply rate on the network. Thus, the suggested method will be used in the design and operation of EIPs to improve their performance.

Fictitious Component Free - Pressure Deficient Network Algorithm for Water Distribution Network with Variable Minimum and Required Pressure-Heads

The pressure-driven analysis is essential for modelling the pressure deficient condition of water distribution networks. Owing to the complexity, the development of pressure-driven analysis algorithms remains a grey area over the past few decades. As a milestone, EPANET 2.0 got upgraded to EPANET 2.2 with the inclusion of pressure-driven analysis. However, EPANET 2.2 has a shortcoming of using only a single value for the parameters, minimum pressure-head and required pressure-head of the demand nodes. Ironically, when a water distribution network serves for a wide area or during a fire-fighting period, the demand nodes have variable values for each of these parameters. To address this, a new method named Fictitious Component Free - Pressure Deficient Network Algorithm (FCF-PDNA) is proposed in this paper. The FCF-PDNA does not require any additional fictitious components. It can be used for both steady-state and extended period simulations. The proposed method is applied to water distribution networks of different sizes and types and confirmed that the FCF-PDNA could deal with variable values of minimum and required pressure-head. The suitability of this method for different scenarios that will lead to pressure deficient conditions is also analysed and verified. Moreover, the computational time taken by the FCF-PDNA and the EPANET 2.2 pressure-driven analysis is similar.

Rural water distribution system with groundwater supply and water tower: Numerical modelling in EPANET 2.2

The paper focuses on the numerical modelling of a rural Water Distribution System (WDS), supplied from a deep well, from which the water is pumped in a water tower (storage tank). Consumers are fed gravitationally from the water tower, with variable demand over 24 hours. Simulations were carried out in EPANET 2.2 using two methods: Demand Driven Analysis (DDA) with outflow issuing from emitters, and Pressure Driven Analysis (PDA). To minimize numerical instabilities, a particular attention was paid to the groundwater well (modelled both with variable, and constant hydrodynamic level), as well as to the connection of the water tower to WDS (where the connection was made either using 2 pipes, or a single pipe). By applying the DDA and PDA methods to the resulting 2×2 configurations of the hydraulic system, a total of 8 sets of simulations (solutions) were obtained and compared. The most advantageous pair of method and configuration is recommended to be considered when modelling a complex (e.g. urban size) WDS with groundwater supply and storage tanks.

Sensitivity Analysis for Performance Evaluation of a Real Water Distribution System by a Pressure Driven Analysis Approach and Artificial Intelligence Method

Proper performance of water distribution networks (WDNs) plays a vital role in customer satisfaction. The aim of this study is to conduct a sensitivity analysis to evaluate the behavior of WDNs analyzed by a pressure-driven analysis (PDA) approach and the classification technique by using an appropriate artificial neural network, namely the Group Method of Data Handling (GMDH). For this purpose, this study is divided into four distinct steps. In the first and second steps, a real network has been analyzed by using a Pressure-Driven Analysis approach (PDA) to obtain the pressure, and α coefficient, the percentage of supplied flow. The analysis has been performed by using three different values of the design peak coefficient k*. In the third step, the Group Method of Data Handling (GMDH) has been applied and several binary models have been constructed. The analysis has been carried out by using input data, including the real topology of the network and the base demand necessary to satisfy requests of users in average conditions and by assuming that the demand in each single one-hour time step depends on a peak coefficient. Finally, the results obtained from the PDA hydraulic analysis and those obtained by using them in the GMDH algorithm have been compared and sensitivity analysis has been carried out. The innovation of the study is to demonstrate that the input parameters adopted in the design are correct. The analysis confirms that the GMDH algorithm gives proper results for this case study and the results are stable also when the value of each k*, characteristic of a different time hour step, varies in an admissible technical range. It was confirmed that the results obtained by using the PDA approach, analyzed by using a GMDH-type neural network, can provide higher performance sufficiency in the evaluation of WDNs.

Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves

AbstractThis technical note presents a technique for the pressure-driven analysis (PDA) of water distribution networks with flow- and pressure-regulating valves. The technique is a combination of a...

A Study on the Practical Pressure-Driven Hydraulic Analysis Method Considering Actual Water Supply Characteristics of Water Distribution Network

For reliable pressure-driven analysis (PDA) results, it is necessary to reasonably determine an objective head-outflow relationship (HOR) and the required head for each node. So far, no methodology has been proposed to objectively determine two factors based on data of real block. In this study, the HOR was defined using the water supply method, residential environment, and water consumption data within real blocks. The standard minimum residual pressure criteria were reviewed to quickly and rationally determine the required head for each node. To validate the proposed methodology, the HOR and required head application conditions were configured for different scenarios; the available flow rate of nodes and the water supply capacity of the entire block were evaluated based on PDA results. Through the results for each scenario, the HOR definition method was able to provide a reasonable result reflecting the actual block’s conditions, unlike the conventional orifice-type HOR, and the standard minimum residual pressure criteria as the required head was evaluated to be more efficient than the conventional time-consuming method. The HOR uncertainty and the lack of rationality in the selection of the required heads affected the reliability of PDA results; these problems can be solved using the proposed methodology.

Flow-based seismic resilience assessment of urban water transmission networks

In this study, a new framework of seismic resilience estimation for urban water transmission networks was developed. The proposed resilience estimation model consists of three phases: input earthquake generation, hydraulic analysis, and recovery of network facilities. In the earthquake generation phase, the uncertainty of the ground motion is determined using the spatially correlated seismic attenuation law. In the hydraulic analysis phase, a hydraulic simulation is performed in conjunction with EPANET analysis. In the recovery phase, network components are restored, and the performance of the recovered network is evaluated through hydraulic analysis. Then, the seismic resilience curve and recovery costs are calculated. For a numerical simulation, a MATLAB-based computer code was developed for pressure-driven analysis in EPANET simulation. To demonstrate the proposed model, an actual water transmission network in South Korea was reconstructed based on geographic information system data. The performance of the network system was evaluated according to two performance indices: system and nodal serviceability. Finally, the cost of repairing the network facilities and water loss are estimated according to earthquake magnitude and interdependency. Numerical results show that the recovery slope of the resilience curve tends to decrease as the earthquake magnitude and interdependency with the power facilities increase.