Optimal Design of Water Distribution Systems Based on Entropy and Topology

A new multi-objective evolutionary optimization approach for joint topology and pipe size design of water distribution systems is presented. The algorithm proposed considers simultaneously the adequacy of flow and pressure at the demand nodes; the initial construction cost; the network topology; and a measure of hydraulic capacity reliability. The optimization procedure is based on a general measure of hydraulic performance that combines statistical entropy, network connectivity and hydraulic feasibility. The topological properties of the solutions are accounted for and arbitrary assumptions regarding the quality of infeasible solutions are not applied. In other words, both feasible and infeasible solutions participate in the evolutionary processes; solutions survive and reproduce or perish strictly according to their Pareto-optimality. Removing artificial barriers in this way frees the algorithm to evolve optimal solutions quickly. Furthermore, any redundant binary codes that result from crossover or mutation are eliminated gradually in a seamless and generic way that avoids the arbitrary loss of potentially useful genetic material and preserves the quality of the information that is transmitted from one generation to the next. The approach proposed is entirely generic: we have not introduced any additional parameters that require calibration on a case-by-case basis. Detailed and extensive results for two test problems are included that suggest the approach is highly effective. In general, the frontier-optimal solutions achieved include topologies that are fully branched, partially- and fully-looped and, for networks with multiple sources, completely separate sub-networks.     

建立给水管网微观动态水力模型标准方法研究

阐述了水司建立给水管网微观动态水力模型的必要性 ,提出了一套适合我国国情的给水管网建模标准方法。这一方法将有助于我国给水管网建模工作走上正规化和科学化的道路。该方法已经成功地应用于上海市。     

Localization of Contamination Sources in Drinking Water Distribution Systems: A Method Based on Successive Positive Readings of Sensors

This paper addresses the problem of the localization of contamination sources after deliberate contaminations in drinking water distribution systems (DWDS). The proposed methodology is based on the information given by successive positive readings of sensors. Thus, it is possible to estimate the localization of the contamination sources based on only the first sensor that detected a contamination, and then update the results when more information is available. From the tests performed on a real drinking water distribution system, it was possible to observe that as new sensors detect changes in contaminant concentration, other possible contaminations may be detected and the location of contamination sources may be more restricted. The results achieved for the two set of sensors considered in the study contained the correct locations and the instants of contaminations previously simulated. Two case studies were also analysed to study the effect of the occurrence of false positives. It was concluded that it is not always possible to verify the occurrence of those anomalies and when it is verified, it is not possible to distinguish between a false positive and a false negative. The occurrence of false positives did not affect also the results related with the real detections.     

复杂供水管网简化计算的研究

提出了一种用于管网简化的新算法 ,其具有可适应各种管网拓扑结构 ,计算结果准确 ,可任意确定管网简化程度的特点。经比较管网简化前后的模型 ,简化精度能够满足管网计算的要求。该算法的实现 ,为供水系统实时优化调度奠定了基础。     

基于理想点法的水质综合评价模型及其应用

理想点法是一种多目标决策分析方法,其核心思想是构造多指标问题的理想解和反理想解,通过计算各指标理想点贴近度,将靠近理想解的程度作为评价依据。将理想点法应用到水质分级综合评价中,采用投影寻踪分析和Delphi法的组合赋权法综合确定指标权重,建立了基于组合赋权-理想点法耦合的综合评估模型。将该模型应用于北京市朝阳区地下水水质综合评价中,并与物元可拓法和投影寻踪模型进行对比分析,结果表明评价结果与实际情况相吻合,该方法应用于水质评价中是可行的。     

基于Monte-Carlo模拟的水工混凝土结构劣化过程分析

水工混凝土结构在工程运行时会发生劣化现象,在未及时修补的情况下将会对工程的功能及正常使用造成不利影响。通过Monte-Carlo模拟的方法可针对不同维修措施的运用随机演化混凝土结构的劣化过程,在经过足够的模拟计算后形成的劣化过程具有一定的精确性和预见性,据此可合理安排结构维修计划,调整维修周期,以实现工程安全运行、节省维修费用的目的。     

轴流式转轮叶片奇点分布法CAD软件设计与研究

现代轴流式转轮叶片设计中，奇点分布法因计算工作量大较少采用，但其理论的严谨性，推导的严密性经常用的统计分析法和升力法更符合流体动力场的客观规律，因而可减少研制新轮转的实验工作量和验证实验数据的可靠性，获得优秀水力模型，本文应用计算机技术，结论 体学理论，进行了奇同流式转轮叶片的ＣＡＤ应用软件的设计与研究。     

Apparent Losses Analysis in District Metered Areas of Water Distribution Systems

As one of the most important component of Non-Revenue Water (NRW), apparent loss exists in all kinds of water distribution system but hardly can be assessed due to its complexity and invisibility. Aimed to analyze the different component of apparent loss on the basis of the characteristic of flow meters in district metered areas (DMA), an effective methodology to calculate the three primary parts of NRW is presented in this paper. In particular, the real loss assessment can be carried out by Minimum Night Flow (MNF) analysis; while the unauthorized consumption can be identified by consuming variation curve; finally, the metering error is calculated by the genetic algorithm with the integrated model based on IWA water balance audit. Application of this method in water distribution network of a steel-making enterprise improves its significance in controlling NRW of DMA.     

Evolving Effective Hydraulic Model for Municipal Water Systems

Constructing a robust hydraulic network model is vitally important, but a time-consuming task. Over last two decades, several approaches using optimization techniques have been developed for identifying model parameters. Although most of the methods can make the model agree with field observations, few are able to achieve a good level of accuracy in terms of determining the correct model parameters for a water distribution system. The previously developed methods appear to be lacking versatility for users to specify calibration tasks given real data for a real system. This paper proposes a comprehensive framework for evolving a hydraulic network model. Calibration tasks can be specified according to data availability and model application requirements. It allows an engineer to (1) flexibly choose any combination of the model parameters such as pipe roughness, junction demand and link (pipes, valves and pumps) operational status; (2) easily aggregate model parameters to reduce the problem dimension for expeditious calculation and (3) consistently specify boundary conditions and junction demand loadings that are corresponding to field data collection. A model calibration is then defined as an implicit nonlinear optimization problem, which is solved by employing a competent evolutionary algorithm. With this methodology, a modeler can be fully assisted to carry out not only a single parameter optimization run, but also a variety of calibration tasks in a progressive manner according to practical system conditions, thus it is possible to achieve a good model calibration with high level of confidence. The method has been applied to the model of a municipal water system to demonstrate the efficacy and robustness of the evolutionary modeling practices.     

长洲水利枢纽水轮机水力性能分析

援引长洲水利枢纽15台机组三个厂家提供的水轮机运转特性曲线及模型综合特性曲线的相关数据进行分析,从而提出三种机型在不同水头下优先选择发电的建议,为确保长洲水利枢纽机组安全稳定运行以及达到增发电量的目的提供技术支持。     

基于内点法的交直流混合系统可用输电能力计算

提出并建立了交直流混合系统可用输电能力优化计算模型,该模型中的混合系统可以包含两端直流系统或多种结构的多端直流系统,模型通用性强。运用非线性原 — 对偶内点法求解模型,在求解过程中,对简约修正矩阵进行行列变换,形成了一种便于存储和编程的数据结构,提高了计算效率。以修改的IEEE 30节点混合系统为算例进行验证,仿真计算表明在换流站进行无功补偿对提高可用输电能力有明显作用,同时也验证了所提出的模型和算法的合理性和有效性。     

Implications of Urban Form on Water Distribution Systems Performance

This paper presents the results of an investigation into the relationship between urban form and the performance of a water distribution system. The effect of new development or redevelopment on the performance of an expanded rehabilitation of the well-known Anytown water distribution system is examined to provide an insight into their interaction, which can be considered along with other aspects of renewal to achieve more sustainable urban areas. A range of urban growth rates, urban form and water efficiency strategies are studied in relation to the system’s key performance indicators of total cost, resilience and water quality. The urban forms considered in this work are compact/uniform, monocentric, polycentric and edge developments. These development patterns are representative of common development approaches widely applied in urban planning. They also correspond to future settlement patterns, based on adopting four future (socio-economic) scenarios so called Policy Reform (PR), Fortress World (FW), New Sustainability Paradigm (NSP), and Market Forces (MF) respectively. Three growth rates and two water demand efficiency levels are considered. It is concluded the rate and type of urban development has major implications for the redesign and operation of existing water infrastructure in terms of total cost, water quality and system resilience, with uniform expansion (PR) resulting in the most cost-effective system upgrade by a considerable margin. Polycentric expansion as a representative urban form for New Sustainability Paradigm is the least cost-effective if it relies on centralised water distribution system to provide service to customers. Edge expansion (MF) has both the cheapest and the most expensive expansion costs depending on location of the expansion. Monocentric urban development (FW) does not result in the most cost-effective system contrary to what has been reported in the literature. Water efficiency measures had relatively little impact on overall performance as it was balanced out with demand increase due to new growth.     

Sustainability Assessment of Urban Water Distribution Systems

A methodology is presented for determining sustainability indices for pressure and water age in water distribution systems (WDSs). These sustainability indices are based upon performance criteria including reliability, resiliency, and vulnerability. Pressure and water age are determined for a WDS as a function of operation time using the U.S. Environmental Protection Agency EPANET model. The values of pressure and water age are used to determine reliability, resiliency, and vulnerability performance criteria, which are then combined into the nodal sustainability indices for water age and pressure. In addition, the sustainability index (SI) computations are performed for zones to define the SI for water age and SI for pressure. A combined SI calculation is performed to produce an overall sustainability score for the entire zone in the water distribution network. The proposed methodology can be used to monitor the sustainability of existing WDSs and to help define alternative solutions including changes in pump operation and modifications to WDS to increase the sustainability.     

Hybrid Genetic Algorithm and Linear Programming Method for Least-Cost Design of Water Distribution Systems

The problems involved in the optimal design of water distribution networks belong to a class of large combinatorial optimization problems. Various heuristic and deterministic algorithms have been developed in the past two decades for solving optimization problems and applied to the design of water distribution systems. Nevertheless, there is still some uncertainty about finding a generally trustworthy method that can consistently find solutions which are really close to the global optimum of this problem. The paper proposes a combined genetic algorithm (GA) and linear programming (LP) method, named GALP for solving water distribution system design problems. It was investigated that the proposed method provides results that are more stable in terms of closeness to a global minimum. The main idea is that linear programming is more dependable than heuristic methods in finding the global optimum, but because it is suitable only for solving branched networks, the GA method is used in the proposed algorithm for decomposing a complex looped network into a group of branched networks. Linear programming is then applied for optimizing every branch network produced by GA from the original looped network. The proposed method was tested on three benchmark least-cost design problems and compared with other methods; the results suggest that the GALP consistently provides better solutions. The method is intended for use in the design and rehabilitation of drinking water systems and pressurized irrigation systems as well.     

基于秩统计量枯水径流分布变点的非参数识别

本文提出了枯水径流时序分布变点的识别原理和基于秩统计量的非参数识别方法，并以东江流域为例，对其干流的枯期径流量年系列（1957-2000年）进行了变点识别，结果显示1974年为东流域枯期径流的显著性分布变点。通过对比分析变点前后的统计参数，1974年后的东江流域枯水径流量年均值明显增加，年际变化的离散程度增大。     

独立覆盖流形法在水工结构分析中的应用前景

针对水工结构有限元分析中存在的网格剖分困难、计算精度不易控制、成果整理工作量大等问题,采用笔者前期提出的独立覆盖流形法,发展了一系列新的分析技术:基于任意形状、任意连接和任意加密的覆盖网格,在保持结构精确几何外形的条件下进行网格自动剖分,结合计算精度控制和成果自动整理,尝试了无需人工参与的自动计算,并为水工结构工程设计与工程分析的融合打下基础;采用解析解与数值解的联合计算方式,提出了坝踵、裂缝尖端等应力奇异区的求解新思路;基于独立覆盖的梁板壳分析,为精确几何的拱坝分析与体形优化、水工薄壁结构分析开辟了新的路径。将来可在模拟水工结构施工、运行过程及考虑多种非线性的仿真分析中实现自动计算,并借助新方法提供稳定可靠的数值分析成果,以实现水工结构分析的标准化、规范化和自动化。     

基于可靠性的两水管道水力设计方法

雨水管道水力设计中,由于影响过水能力的各水力因子具有不确定性,从而导致过水能力为随机变量,过水能力能否满足设计雨水流量是一随机事件.在阐明水力因子、过水能力的概率分布和统计参数的基础上,提出了基于可靠性的雨水管道水力设计方法,并给出了计算示例.     

高水头水轮机配水环管(蜗壳)水压试验及保压浇筑混凝土

高水头冲击式水轮机配水环管（蜗壳）采用分段压力试验,消除大厚度钢板焊接过程中产生的应力;大型中高水头抽水蓄能机组也采用水压试验来有效消除蜗壳焊接过程中的应力并检查焊接质量,同时检验蜗壳充水后的变形规律。两种类型机组的配水环管和蜗壳均采用保压浇筑混凝土施工的方法,取消蜗壳与混凝土之间的弹性垫层,使蜗壳与混凝土紧贴,减小机组运行中的振动,减小蜗壳内水压力对混凝土的作用力,增加安全裕度。     

Topographic Energy Management in Water Distribution Systems

A significant amount of energy is required to operate pressurised water distribution systems, and therefore, improving their efficiency is crucial. Traditionally, more emphasis has been placed on operational losses (pumping inefficiencies, excess leakage or friction in pipes) than on structural (or topographic) losses, which arise because of the irregular (unchangeable) terrain on which the system is located and the network’s layout. Hence, modifying the network to adopt an ecologically friendly layout is the only way to reduce structural losses. With the aim of improving the management of water distribution systems and optimising their energy use, this work audits and classifies water networks’ structural losses (derived from topographic energy), which constitutes the main novelty of this paper. Energy can be recovered with PATs (pumps as turbines) or removed through PRVs (pressure reducing valves). The proposed hydraulic analysis clarifies how that energy is used and identifies the most suitable strategy for improving efficiency as locating the most suitable place to install PRVs or PATs. Two examples are discussed to illustrate the relevance of this analysis.