Decision support system to divide a large network into suitable District Metered Areas

This paper presents a new approach to divide large Water Distribution Networks (WDN) into suitable District Metered Areas (DMAs). It uses a hydraulic simulator and two operational models to identify the optimal number of DMAs, their entry points and boundary valves, and the network reinforcement/replacement needs throughout the project plan. The first model divides the WDN into suitable DMAs based on graph theory concepts and some user-defined criteria. The second model uses a simulated annealing algorithm to identify the optimal number and location of entry points and boundary valves, and the pipes reinforcement/replacement, necessary to meet the velocity and pressure requirements. The objective function is the difference between the economic benefits in terms of water loss reduction (arising from the average pressure reduction) and the cost of implementing the DMAs. To illustrate the proposed methodology, the results from a hypothetical case study are presented and discussed.     

An Automated Tool for Smart Water Network Partitioning

Water Network Partitioning (WNP) represents the application of the “divide and conquer” paradigm to a Smart WAter Network (SWAN) that allows the improved application of techniques for water balance and pressure control. Indeed, these techniques can be applied with greater effectiveness by defining smaller permanent network parts, called District Meter Areas (DMAs), created by the insertion of gate valves and flow meters. The traditional criteria for the design of network DMAs are based on empirical suggestions (number of properties, length of pipes, etc.) and on approaches such as ‘trial and error’, even if used together with hydraulic simulation software. Nevertheless, these indications and procedures are very difficult to apply to large water supply systems because the insertion of gate valves modifies the original network layout and may considerably worsen the hydraulic performance of the water network. The proposed tool, based on some graph partitioning techniques, commonly applied in distributed computing, and on an original optimisation technique, allows the automatic design of a WNP comparing different possible layouts that are compliant with hydraulic performance. In this paper, the methodology was tested on a real case study using some performance indices to compare different WNPs. The proposed tool was developed in Phyton and integrates graph partitioning, hydraulic simulation techniques and a heuristic optimisation criterion. It allows the definition of DMAs with resulting performance indices that are very similar to the original network layout.     

Modularity-Based Procedure for Partitioning Water Distribution Systems into Independent Districts

A proper division of a Water Distribution System (WDS) into District Metered Areas (DMAs) provides important management benefits particularly with regard to leakage detection through water balances, control and optimization of pressure so as to reduce leakage, implementation of monitoring, warning and emergency acting systems against accidental or intentional water contamination. This paper presents a new methodology that combines a suitable modularity-based algorithm for the automated creation of DMA boundaries and convincing practical criteria for the DMA design. A further plus of the proposed methodology is its ability to identify many technically feasible solutions that can be subsequently economically assessed. The successful applications of the proposed methodology to a real case study, already tested by other authors, has proven its effectiveness for the DMA design in existing water distribution systems.     

District Metered Areas Design Under Different Decision Makers’ Options: Cost Analysis

Water loss is a big challenge for water supply companies worldwide, and the Water Network Partitioning (WNP) is an excellent tool for water loss management–particularly in the current difficult economic and financial conditions. WNP is a recent research line and consists in dividing the water distribution network into smaller zones called District Metered Areas (DMAs) with one (or more, in exceptional cases) supply point, to reduce the network complexity and/or allow pressure management. Since there are several possible future scenarios, such as the water demand and/or the infrastructure degradation forecasts, which may have different impacts on the hydraulic behaviour, in this paper a computational application, based on an optimization model, is proposed to achieve a compromise between robustness required for the DMAs design (using a baseline scenario) and different decision makers’ options (using other scenarios with a lower “probability” of occurrence), to reduce the total cost. The objective function reflects the minimization of the squared deviations between the total cost of the DMAs design and the minimum cost for each scenario forecasted for the project plan, multiplied by the weight or “probability” of occurrence for each of the scenarios. The performance of the computational application is illustrated with a case study, and the results are encouraging.     

Automatic Multiscale Approach for Water Networks Partitioning into Dynamic District Metered Areas

Water distribution systems (WDSs) today are expected to continuously provide clean water while meeting users demand, and pressure requirements. To accomplish these targets is not an easy task due to extreme weather events, operative accidents and intentional attacks; as well as the progressive deterioration of the WDS assets. Therefore, water utilities should be ready to deal with a range of disruption scenarios such as abrupt variations on the water demand e.g. caused by pipe bursts or topological changes in the water network. This paper presents a novel methodology to automatically split a WDS into self-adapting district metered areas (DMAs) of different size in response to such scenarios. Complex Networks Theory is proposed for creating novel multiscale network layouts for a WDS. This makes it possible to automatically define the dynamic partitioning of WDSs to support further DMA aggregation / disaggregation operations. A real, already partitioned, water utility network shows the usefulness of an adaptive partitioning when the network is affected by an abnormal increase of the peak demand of up to 15%. The dynamic DMA reuses the assets of the static partitioning and, in this case, up to the 82% of resilience is restored using 94% of the assets already installed. The results also show that the overall computational and economic management costs are reduced compared to the static DMA partition while the hydraulic performance of the WDS is simultaneously preserved.

     

Water Saving and Energy Reduction through Pressure Management in Urban Water Distribution Networks

Water shortages and climate change are worldwide issues. Reduction in water leakage in distribution networks as well as the associated energy saving and environmental impacts have recently received increased attention by scientists and water industries. Pressure management has been proposed as a cost-effective approach for reduction in water leakage. This study conducted a real-world water pressure regulation experiment to establish the pressure-leakage relationship in a district metering area (DMA) of the water distribution network in Beijing, China. Results showed that flow into the DMA was sensitive to inlet water pressure. A 5.6 m reduction in inlet pressure (from 38.8 m to 33.2 m) led to an 83 % reduction (12.1 l/s) in minimal night flow, which is a good approximator of leakage. These reductions resulted in 62,633 m³ of water saved every year for every km pipe, as well as associated savings of 1.1?×?10⁶ MJ of energy and 68 t of CO₂ equivalent greenhouse gas emissions. The results of this study provide decision makers with advice for reducing leakage in water distribution networks with associated energy and environmental benefits.     

Pressure Management Through Optimal Location and Setting of Valves in Water Distribution Networks Using a Music-Inspired Approach

Pressure management through Pressure Reducing Valves (PRVs) is probably the most used approach related to the leakage management in Water Distribution Networks (WDNs). Its effectiveness in reducing the amount of water losses in existing networks has been highlighted in many papers. In this study, the topic is addressed with particular reference to meta-heuristic optimization techniques, that have proved to be very effective in producing good results with reduced use of computational resources. In particular, the application of the Harmony-Search (HS) method to the location and setting of a pre-fixed number of PRVs is proposed and discussed. A single objective optimization problem is defined which aims at the leakage reduction through the minimization of the water pressures. A double harmonic component is adopted for taking into account both the location and the setting of each PRV. The hydraulic constraints handled by a simulation software are considered as well. The approach is applied to a couple of WDNs: one is the Jowitt and Xu well-known literature test case and the other is a real WDN in Naples, called Napoli Est. The methodology has showed very good results compared to those obtained by using classical Genetic Algorithm techniques both in terms of leakage reduction and computation time.     

带差动挑坎的溢洪道流场三维数值模拟

采用RNGκ-ε紊流模型和VOF方法对某工程带差动型挑坎的溢洪道流场进行了三维数值模拟研究,详细描述了差动坎处的流速、压强等水力参数的分布规律,得出了高低坎挑射水舌的挑距、入水角。将部分结果与试验对比,符合良好,验证了数值模拟是准确可靠的,可作为模型试验的有益补充,为挑坎设计提供重要的参考依据。     

Optimal Location and Setting of PRVs in WDS for Leakage Minimization

Water loss is an issue that affect Water Distribution Systems (WDSs) very often, especially when aged and high pressure occurs. Pressure reduction valves (PRVs) can be used as devices to reduce as much as possible the water losses within the network. Indeed, for a given number of PRVs, the daily volume of water lost from the network can be reduced minimizing the pressure through a proper choice of valve positions as well as their settings. In this paper, a methodology for the optimal number, positioning and setting of PRVs is presented. In the proposed methodology, a genetic algorithm is coupled with a physical modelling of leakage from joints and a simplified and yet realistic hydraulic simulation of the WDS. The proposed methodology is demonstrated using two WDSs examples. Comparisons with a more extreme and complicated hydraulic modelling, already proposed by authors in previous work, are also performed in the first case study in order to validate the proposed methodology. These comparisons demonstrate that the methodology proposed in this work performs fairly well when compared to similar approach that uses a more sophisticated hydraulic model. As a consequence, it revealed to be a good tool for the optimal positioning and sizing of PRVs within WDS aimed at reducing the background leakages even when the WDS is characterized by complex geometry and topology.     

南水北调中线工程总干渠水力学 仿真模型研究

以节制闸为边界将南水北调中线总干渠分为若干子段,采用闸门过闸流量公式、能量方程、圣维南（Saint-Venant）方程组和低压管流方程分别计算闸门水位流量关系、明渠恒定流、明渠非恒定流和有压建筑物非恒定流,以此建立总干渠水力学计算模型。通过双重迭代方法对水流方程、过闸流量方程进行联合求解,以模拟总干渠运行调度动态过渡过程,以京石段2008年输水实测数据对水力学模型进行验证,结果表明模型具有良好的收敛性和较高的精度。     

Calibration Model for Water Distribution Network Using Pressures Estimated by Artificial Neural Networks

The success of hydraulic simulation models of water distribution networks is associated with the ability of these models to represent real systems accurately. To achieve this, the calibration phase is essential. Current calibration methods are based on minimizing the error between measured and simulated values of pressure and flow. This minimization is based on a search of parameter values to be calibrated, including pipe roughness, nodal demand, and leakage flow. The resulting hydraulic problem contains several variables. In addition, a limited set of known monitored pressure and flow values creates an indeterminate problem with more variables than equations. Seeking to address the lack of monitored data for the calibration of Water Distribution Networks (WDNs), this paper uses a meta-model based on an Artificial Neural Network (ANN) to estimate pressure on all nodes of a network. The calibration of pipe roughness applies a metaheuristic search method called Particle Swarm Optimization (PSO) to minimize the objective function represented by the difference between simulated and forecasted pressure values. The proposed method is evaluated at steady state and over an extended period for a real District Metering Area (DMA), named Campos do Conde II, and the hypothetical network named C-town, which is used as a benchmark for calibration studies.     

基于贝叶斯理论的城市供水管网泄漏在线检测与定位

许多城市的供水管网都安装了SCADA(Supervisory Control And Data Acquisition)系统,基于SCADA系统监测到的数据可对管网泄漏进行检测。通过引进统计学概率论中一基本定理——贝叶斯定理来建立管网泄漏的在线检测与定位模型,一定程度上解决了水力模拟误差、测量误差、测点配置等因素导致的不确定性问题。模型通过实例考核取得较为满意的诊断结果。     

水轮机蜗壳的优化设计与CFD分析

采用变速度矩法进行水轮机蜗壳的水力设计,在此基础上以变速度矩系数为设计变量,以蜗壳水力损失最小为目标函数建立数学模型,应用混合惩罚函数法针对实例进行优化设计,采用CFD数值模拟计算,将优化设计结果与传统设计结果进行比较分析,结果表明:采用变速度矩法设计的蜗壳尾端压力和水流流速都分布均匀,水力损失小,性能优越。     

基于高压压水试验的裂隙岩体非线性渗流参数解析模型

高渗压条件下裂隙岩体的渗透特性是高压引水隧洞近场渗流场分析与工程防渗设计的重要参数,一般通过现场钻孔高压压水试验获得。针对钻孔高压压水试验流量-压力曲线的非线性特征,建立了基于Forchheimer方程的裂隙岩体非线性渗流参数(渗透系数k和非线性系数b)解析模型。该解析模型中的渗透系数解析表达式与现行钻孔压水试验规程推荐公式一致,不仅形式简洁,而且物理意义明确,是现行规程推荐公式在非线性流条件下的拓展,可作为高压压水试验条件下钻孔压水试验规程修订的重要依据。对海南省琼中抽水蓄能电站高压岔管区钻孔高压压水试验成果的分析表明:Forchheimer方程很好地表征了高压压水试验过程中流量-压力曲线的非线性特征,本文提出的解析模型为高渗压条件下裂隙岩体非线性渗流参数的合理取值提供了有效的方法和手段,克服了现行钻孔压水试验规程对高渗压条件下裂隙岩体渗透性难以正确表征的局限和由此带来的工程防渗设计风险。     

无黏性土管涌的临界流速

根据多孔介质中的变截面管模型,分析单个颗粒在孔隙通道中的受力情况,建立力的平衡方程,从而推导出管涌发生时的水流临界流速公式。结合试验对该公式进行了验证,当作用于水流的拖曳力与静水压力的作用大于阻碍其运动的作用时,认为可动颗粒开始起动。算例分析表明,运用临界流速公式能够准确地预测土体的管涌破坏。     

水电站水力过渡过程数值仿真的理论与实践

系统地介绍了水电站水力过渡过程数字仿真的基本理论和计算方法,过渡过程的起因和研究内容,并用多个水工模型试验测量的调压室水位、管道水锤压力及其压力过程线资料验证了计算方法及参数选择的合理性.利用CTD技术得到了调压室内的水流流态、三维流速分布以及调压室水位波动的动态演示.该数字模型已用于多个电站引、尾水系统的水力过渡过程计算,得到的调压室最高/最低涌浪水位、蜗壳及岔管断面最大/最小水锤压力、机组最大飞车转速以及它们的变化过程线,引水隧洞最大/最小内水压力包络线、小波动和水力干扰下的发电频率摆动、机组稳定性分析等成果,为工程设计提供了重要依据.     

Optimal Pressure Regulation in Water Distribution Systems Based on an Extended Model for Pressure Reducing Valves

Optimal pressure regulation to reduce water losses in water distribution systems (WDSs) becomes an important concern due to the increasing water demand and the threat of drought in many areas of the world. The leakage amount in a WDS depends heavily on its operating pressure and thus can be minimized by implementing optimal pressure strategies through pressure reducing valves (PRVs). To achieve this, a model-based optimization is necessary, where an accurate model of the PRVs is required. The PRV models having been used until now for pressure regulations are two-mode models which cannot circumstantiate many situations occurring in WDSs. In this paper, we extend the existing model by a three-mode one for PRVs which is able to describe the required circumstances of pressure regulations in WDSs. The non-smoothness of this model is smoothed by an approximation approach, thus allowing the formulation and solution of a continuous nonlinear optimization problem for optimal pressure regulation. Two benchmark WDSs are used to verify our approach and it can be shown from the results that our PRV model outperforms the existing models in terms of the quality and accuracy of the optimal solutions.

     

突扩突跌掺气设施后泄槽底板脉动压力试验研究

有压洞出口后的突扩突跌掺气减蚀设施在水利工程中经常使用。由于水流受边界条件和掺气的影响,其流态和脉动压力往往与普通水槽的情况有很大的不同。通过水工模型试验,对突扩突跌掺气设施后泄槽底板上的脉动压力进行研究,揭示了掺气设施后泄槽底板上不同流动区域的脉动压力特性。从脉动压力的时域过程、均方根值、偏态系数、峰态系数和主频率等多方面得出冲击区、反射区和稳定区脉动压力的特性是不相同的结论。同一流量时,沿流程底板的时均压力都大于脉动压力的均方根值,在冲击区、反射区和稳定区,脉动压力的均方根值分别是同位置时均压力值的约0.5倍、0.6倍和0.7倍。研究成果可为更好地利用突扩突跌掺气设施提供有益的理论和试验依据。     

Research of the performance of pulse electrohydrodynamics in blockage removal

In line with contemporary trends and seeking to develop new methods and technologies, a new, original technology was explored and designed based on a non-conventional process of electrical pulse discharge in a water chamber, referred to as 'Pulse Electrohydrodynamic Technology' (PELHYDT). The application of the PELHYDT in sewer blockage removal is presented in this paper. Existing machinery can remove two blockages of gully pot connections per hour. Three blockages of pipe conduits are generally removed during an 8-h working day. Applying PELHYDT technology, which allows for high rates of removal of mechanical obstructions, it is possible to achieve operating fluid pressures in the order of 10(3)-10(4) bars, a velocity of 100 m/s, a deformation acceleration of the model material structure of 10(6)-10(7) m/s2, and high-frequency hydraulic shock waves with a frequency of 10(3)-10(4) Hz. The applicability of this efficient technology in sewer blockage removal was proven under laboratory conditions at operating fluid pressures from 50 to 160 bars, which are standard for sewer maintenance. Water velocities generally achieved in sewers using existing flushing technologies range between 1 and 3 m/s and usually do not exceed 9 m/s. PELHYDT creates waves whose velocity is at least 100 m/s, and is therefore about ten times more efficient than existing technologies. PELHYDT generates an electrohydrodynamic wave very quickly, virtually in the form of an explosion. It was proven under laboratory conditions that the application of this technology for blockage removal in practice will not result in any sewer damage.     

引江补汉工程段中分层减压控制闸布置与体型研究

引江补汉工程段中控制方案将控制闸设置在 164?km 处，以避免局部段内压过高的问题，主要从水动力特性 的角度论证洞线总体布置及控制闸布置与体型的合理性。采用一、三维数学模型与物理模型相结合的复合模型 开展相关研究：一维水锤数学模型用于闸门启闭过程的全线水力过渡过程分析，通过优化计算，得到相对较优的 闸门启闭过程，同时为控制闸段的三维数模与物理模型提供边界条件；三维水气两相流数学模型与物理模型模拟 分析闸室与调流池流态与水面波动、中孔溢流面压力分布等水力指标，同时为一维数学模型提供控制闸泄流能力 曲线。结果表明：当控制中孔弧形门以先慢后快的三阶段变速率过程开启时，可将全线的最大水锤压力压值在规 程允许范围内；中孔溢流面压力分布正常，调流池内水体消能充分，下有压洞进口前沿水面波动较小，未见吸气旋 涡等不利流态。引江补汉工程工程采用段中分层减压控制的总体方案是可行的，控制闸布置与体型合理，研究方 法可供类似工程参考。