Water Transmission Network Research Articles

Leak Detection in Water Collection and Transmission Networks Using the Minimum Nodal Pressure Measurement

Leak has always been one of the problems in water distribution networks, whose preventing not only results in the saving of water sources but also has profound effects on the maintenance cost of networks. In the present paper, a new method is applied for leak detection in water collection and transmission network. In this method, detection of leak location is performed by pressure difference analysis at junctions and by the help of the relative index of the leak. The pressure measurements should be performed at least at two nodes for two cases of with and without the presence of leak. The minimum number of pressure measurements to form a relative leak index is two. However, in this case, two nodal pressure measurements are too few, and the number of pressure measurement should be increased. Therefore the next option for the number of measurements is three. The investigated network in this research includes 7 wells with an approximate length of 7800 m located in the northwestern city of Mashhad. A real leak with a rate of 7.57 l/s is created at one of the network nodes whose amount is measurable by a volume counter. The real leak is a hypothetical leak which is known in advance, and its magnitude is not necessarily a round number in term of a liter per second. Finally, this leak is identified by the proposed method via 3 nodal pressure measurements.

Classification of major cohorts of Australian pressurised cast iron water mains for pipe renewal

Cast iron pipes buried between the 1860s and 1980s still account for a significant proportion of the Australian water transmission network, and failure rates of cast iron trunk mains have risen in the past decades. In Australian cities, the manufacturing methods and corrosion mitigation techniques used in cast iron pipes are strongly correlated with the pipeline burial year. This paper introduces an approach to summarise the remaining in service cast iron trunk mains into several cohorts, in order to identify the critical pipelines with high potential of longitudinal fracture in pipe barrels. Despite the various manufacturers and casting moulds used in Australian cast iron pipes, two major cohorts, static and spun cast iron pipes, were identified based on manufacturing methods, material properties, microstructural analysis and wall thicknesses. A statistical analysis confirmed that spun cast pipes have higher burst rates and relatively short life spans than statically cast pipes, evidently due to thinner wall size.

A Comparison on Discharge Coefficients of Side and Normal Weirs with Suspended Flow Load using FLOW3D

Normal 0 MicrosoftInternetExplorer4 Weirs and gates are structures which are used to measure water flow in open channels. Entering rivers’ sediments into channels is considered as one of the main problems in irrigation and water transmission networks. The relations presented based on laboratory results for gates, weirs and apertures’ discharge coefficients have been extracted and developed based on the conditions of sediment free water flow. Therefore, applying these relations in natural conditions requires investigating the effect of suspended load on hydraulic coefficients which are highly effective to technically and economically design and select these structures. The purpose of the present paper was to determine the amount of flow discharge and the type of effective parameters using different geometrical and hydraulic conditions such as overflow height. It was also attempted to present the relation of discharge coefficient at the presence of suspended load. To this end, three-dimensional FLOW 3D model was employed. This numerical model can simulate the flow containing suspended sediments and sediments’ deposition in various parts of channel. In numerical simulation, based on landing number of flow, C d has a determination coefficient (R 2 ) relatively better and higher than laboratory results. It can be attributed to the lack of suspended load thickness distribution in laboratory and difficult conditions of such action in laboratory modeling. In laboratory model, suspended load cannot be fully injected with appropriate ratio to the entire fluid. However, in numerical model, flow thickness amount can be easily added an injected to the model from input boundary on cubic meter unit of flow. This significant point is considered as one of the advantages of numerical model to simulate such problems. In the present study, total relation of flow discharge (C d ) was presented as a combination of values of flow landing (F r ), flow thickness amount (S) and relative low depth (y d /P) in side weirs. st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Calibri; mso-bidi-font-family:Calibri;}

Skeletonization Methods for Complex Water Distribution Network

Studies of optimizing pump operation in water distribution networks (WDN) are receiving spotlight in recent days. However, the water networks are quite complex including thousands of or even tens of thousands of nodes and pipes, thus simulation time is an issue. In some cases, implementing a computer model for pump operation decisions is restrictive due to intensive computation time. To that end, it is necessary to reduce the simulation time of water networks by simplifying the network layout. In this study, WDN skeletonization approaches were suggested and applied to a real water transmission network in South Korea. In skeletonizing the original network, it was constrained to match the water pressure and water age in the same junction locations to maintain the hydraulic and water quality characteristics in the skeletonized network. Using the skeletonization approaches suggested in this study, it is expected to reduce the simulation time of WDN and apply for developing a computer module of WDN real-time optimal operation.

Convex reformulations for solving a nonlinear network design problem

We consider a nonlinear nonconvex network design problem that arises, for example, in natural gas or water transmission networks. Given is such a network with active and passive components, that is, valves, compressors, control valves (active) and pipelines (passive), and a desired amount of flow at certain specified entry and exit nodes in the network. The active elements are associated with costs when used. Besides flow conservation constraints in the nodes, the flow must fulfill nonlinear nonconvex pressure loss constraints on the arcs subject to potential values (i.e., pressure levels) in both end nodes of each arc. The problem is to compute a cost minimal setting of the active components and numerical values for the flow and node potentials. We examine different (convex) relaxations for a subproblem of the design problem and benefit from them within a branch-and-bound approach. We compare different approaches based on nonlinear optimization numerically on a set of test instances.

Real-time pump scheduling for water transmission systems: Case study

This study develops a real-time near-optimal pump scheduling model for water transmission networks. The model aims to minimize energy cost by means of optimal pump operation while meeting system demands and satisfying operational constraints. The real-time control is realized using Supervisory Control and Data Acquisition (SCADA) system, by which system monitoring data is collected and the optimal control decisions are sent to the pumping stations for implementation. The model is composed of three simulation modules, such as demand forecasting, hydraulic simulation, and optimization. Decision variables include pump on/off (binary code of 0/1) schedules for fixed-rate pumps for each time-step over pre-defined operation time horizon. Various operational constraints are embedded in the model reflecting real operational practices. The proposed optimization model is demonstrated using a real, medium-sized water transmission system in Seoul, South Korea and showed 19~27% energy cost savings compared to a conventional operation scheme.

Seismic reliability assessment of lifeline networks using clustering‐based multi‐scale approach

SummarySeismic reliability assessment of lifeline networks gives rise to various technical challenges, which are mostly caused by a large number of network components, complex network topology, and statistical dependence between component failures. For effective risk assessment and probabilistic inference based on post‐hazard observations, various non‐simulation‐based algorithms have been developed, including the selective recursive decomposition algorithm (S‐RDA). To facilitate the application of such an algorithm to large networks, a new multi‐scale approach is developed in this paper. Using spectral clustering algorithms, a network is first divided into an adequate number of clusters such that the number of inter‐cluster links is minimized while the number of the nodes in each cluster remains reasonably large. The connectivity around the identified clusters is represented by super‐links. The reduced size of the simplified network enables the S‐RDA algorithm to perform the network risk assessment efficiently. When the simplified network is still large even after a clustering, additional levels of clustering can be introduced to have a hierarchical modeling structure. The efficiency and effectiveness of the proposed multi‐scale approach are demonstrated successfully by numerical examples of a hypothetical network, a gas transmission pipeline network, and a water transmission network. Copyright © 2014 John Wiley & Sons, Ltd.

Efficient risk assessment of lifeline networks under spatially correlated ground motions using selective recursive decomposition algorithm

SUMMARYFor effective hazard mitigation planning and prompt‐but‐prudent post‐disaster responses, it is essential to evaluate the reliability of infrastructure networks accurately and efficiently. A nonsimulation‐based algorithm, termed as a recursive decomposition algorithm (RDA), was recently proposed to identify disjoint cut sets and link sets and to compute the network reliability. This paper introduces a ‘selective’ RDA, which preferentially identifies critical disjoint cut sets and link sets to calculate the probabilities of network disconnection events with a significantly reduced number of identified sets. To this end, the original RDA is improved by replacing the shortest path algorithm with an algorithm that identifies the most reliable path, and by using a graph decomposition scheme based on the probabilities associated with the subgraphs. The critical sets identified by the algorithm are also used to compute conditional probability‐based importance measures that quantify the relative importance of network components by their contributions to network disconnection events. This paper also introduces a risk assessment framework for lifeline networks based on the use of the selective RDA, which can consider both interevent and intraevent uncertainties of spatially correlated ground motions. The risk assessment framework and the selective RDA are demonstrated by a hypothetical network example, and the gas and water transmission networks of Shelby County in Tennessee, USA. The examples show that the proposed framework and the selective RDA greatly improve efficiency of risk assessment of complex lifeline networks, which are characterized by a large number of components, complex network topology, and statistical dependence between component failures. Copyright © 2012 John Wiley & Sons, Ltd.

Optimal Dimensioning of Pipe Networks with Application to Gas Transmission Networks

We develop an algorithm to solve the problem of the optimal dimensioning of a fluid (gas or water) transmission network when the topology of the network is known. The pipe diameters must be chosen to minimize the sum of the investment and operating costs. This two stage problem is solved by application of the bundle method for nonsmooth optimization. The validity of the approach is tested on a problem corresponding to a real situation: the optimal design of a reinforcement of the Belgian gas network.

Optimization of underground water transmission network systems under seismic risk

The purpose of this paper is to establish procedures for the optimum design of underground water transmission systems to be newly constructed as well as for the optimum improvement of existing systems on the basis of seismic risk and cost-effectiveness considerations. As an example, a realistic water transmission system will be analyzed and optimized. Procedures for optimizing the total cost are developed in which the pipe diameters and the network topology are parameters which can be varied to achieve a minimum total cost under certain realistic constraints. The total cost includes the initial cost premium, repair costs and incident (fire) costs. The optimization algorithm employed in this study is derived from the discrete gradient method.

Some Aspects of Seismic Risk Analysis of Underground Lifeline Systems

The current state of the art of the seismic risk analysis for the underground lifeline systems, particularly for the water transmission network system, is reviewed. An emphasis in the review is placed on the analysis of major causes of system damages and on the procedures of the seismic design decision analysis unique to the underground lifeline systems. A methodology of the seismic risk analysis is then developed and an example analysis performed for a simplified version of the water transmission system in the City of Los Angeles indicating each step of the analysis and each assumption used therein. The example analysis has been carried through to the point where a sample of physically damaged network systems are simulated by means of a Monte Carlo technique. Eventually, a topological analysis should be applied to such a sample of damaged systems to estimate the probability of the original system becoming unserviceable immediately following an earthquake of a given intensity. Such probability values are vitally needed for the ultimate purpose of design decision analysis.