Testing behavior and effects of PRVs and RTC valves during hydrant activation scenarios

This paper provides an insight into behavior and effects of pressure reducing valves (PRVs) and of valves controlled in real time (RTC) during hydrant activation scenarios, which determine high-flow conditions in water distribution networks (WDNs). The analysis is carried out through the pressure-driven unsteady flow modeling of an Italian WDN, in which a pressure control device is assumed to be installed in the pipe outgoing from the source. Scenarios are constructed considering alternatively a PRV or an RTC valve, as pressure control device, and two different sites for hydrant activation. The results highlight that, thanks to its capability of controlling the service pressure at the critical node, the RTC valve performs better than the PRV, which is regulated based on its outlet pressure. In fact, the adoption of the RTC valve attenuates pressure deficits in the network, above all when the control time step is suitably small to attenuate pressure head oscillations at the controlled node. An additional benefit of RTC lies in increased outflows from the hydrant. The benefits of the RTC valve are smaller when the hydrant is activated in more redundant parts of the network, where pipe water discharge variations put the system to a less severe test.     

Design strategy to maximize recovery energy towards smart water grids: case study

Water distribution networks (WDNs) appear as a new opportunity to generate clean energy using pumps working as turbines (PATs) instead of pressure reduction valves (PRVs). This research presents a strategy for maximizing the recovered energy, and the development of a deep feasibility analysis, enabling the selection of the best scenario and operation mode. A design for a strategy to create an acceptable PAT working in a water distribution network and maximizing energy production, without affecting the water distribution service, is presented. The characteristic parameters of the system are described, evaluating efficiency, capabilities, reliability and sustainability. In addition, an economic analysis of the project was made to evaluate the viability of PAT implementation. The total energy production in this case study was 485 MW?h/year; and the feasibility indexes, internal rate of return, benefit/cost ratio and payback period were 0.79, 8.2 and 2 years, respectively.     

An economic valuation model for alternative pressure management schemes in water distribution networks

Pressure management (PM) is commonly used in water distribution networks (WDNs) to provide a wide range of benefits. This study presents an economic evaluation framework to support the decision-making process relating to alternative PM schemes. The methodology allows for the assessment the principal direct and indirect benefits and costs associated with using pressure-reducing valves (PRVs). The methodology is applied to a district metered area in a WDN in Mashhad, Iran, by changing the existing fixed–outlet (FO-PRV) to time-based (TM-PRV) and flow-based modulation (FM-PRV). The results indicated that FM-PRV is the most beneficial scheme for the studied case. The importance of estimating direct and indirect benefits is highlighted. The presented methodology is essential to persuade water utility decision-makers to recognize the economic feasibility and significant benefits of implementing PM schemes and justify the associated investment.     

缺少观测地区地下水位统测方案优化设计

地下水位统测数据属于基础性资料,可为区域水文地质编图提供重要依据,也是地下水数值模拟建立初始流场的必要数据.部分地区由于缺少观测资料,布置地下水位统测点比较困难.针对这一难题,本文提出了一种设计、优化地下水位统测网的方法:首先通过密网格数值模拟获得参考地下水位等值线图,再根据初步设计的若干水位统测方案,进行水位采样作为...     

基于随机多项式展开的流固耦合非饱和土坡概率反分析

降雨入渗条件下非饱和土坡流固耦合作用复杂,具有高度非线性的特点,一般采用数值方法模拟。数值模型计算量大已成为监测数据概率反分析的重要制约因素。提出一种基于随机多项式展开(PCE)的概率反分析方法。该方法采用随机多项式展开构建土性参数与数值模型响应的显式函数,作为概率反分析中原数值模型的代替模型,与基于贝叶斯理论和马尔可夫链蒙特卡罗(MCMC)模拟的概率反分析方法相结合,从而有效提高非饱和土坡流固耦合参数概率反分析的效率。通过降雨入渗非饱和土坡算例研究,结果表明,与基于数值模型的常规随机反分析相比,两种方法在后验分布统计值、95%置信区间等结果非常接近,基于PCE的概率反分析计算效率显著提高,结果可靠。     

Accounting for uniformly distributed pipe demand in WDN analysis: enhanced GGA

The global gradient algorithm (GGA) is the most widely adopted method for steady-state analysis of water distribution networks. It is used to solve the non-linear system of equations describing mass and energy conservation laws. Nonetheless, it has been recently proved that the usually adopted representation of distributed pipe demands as lumped withdrawals at ending nodes causes inconsistent calibration results and pipe head loss errors which could be non negligible in some network conditions. The original GGA has been contextually modified by introducing a correction of pipe hydraulic resistance under the assumptions of a friction factor independent from the flow regime. This paper aims at providing researchers and software developers with a general formulation of the GGA which entails both the adoption of any generic monomial head loss formula and pipe hydraulic resistance dependence on flow regime. The results could be easily extended to other methods of network analysis.     

Aerodynamic and water penetration investigations upon pitched roof vents

Pitched roof vents (PRVs) can be used both to extract air into the atmosphere (‘blowing’) and to draw in fresh air (‘sucking’). In both of these situations, the PRV facilitates the exchange of air between the inside and outside of a building. Photographs of typical generic PRV designs are presented. As shown in these photographs, PRVs are mounted within a pitched roof, and may or may not protrude slightly above the roof surface. Hence their performance is likely to be influenced strongly by wind flowing above and around the roof. The internal and external design of PRVs is complex, and PRVs are designed to strike a balance between aerodynamic efficiency, weather-tightness performance, and cost of manufacture.Experiments have been undertaken at Building Research Establishment (BRE) to test the weather-tightness and aerodynamic performance of PRVs. This paper describes the test rig and the methods used to obtain experimental results. A particular feature of this test rig is that it is able to discriminate between leakage through the PRV, the roof covering, and the interface between the roof covering and the PRV.A wide range of UK domestic and industrial marketplace PRV products were tested. For the aerodynamic performance tests, typical results are presented for different wind speeds and different roof pitch angles. An empirical equation is presented that was found to describe well the aerodynamic performance of every PRV tested. For the weather-tightness tests, a new visual criteria is suggested which, although subjective in nature, provides very useful information about water penetration that cannot be obtained in any other way. A typical weather-tightness plot is presented that uses the new visual criteria, together with the more traditional method of weighing the water ingress. For both the aerodynamic and weather-tightness tests, the findings and conclusions of the overall test programme are presented.     

自来水用户用水模式的确定方法研究

针对管网建模过程中用水量变化规律的复杂性,提出了根据实际用水量数据进行聚类分析,合理地对用户进行分类的方法,并通过主成分综合模型确定了每一类用户典型的用水模式曲线.该方法借助电磁水表实时远传的水量数据,能够及时更新用户的用水模式曲线,为提高建模的精确性打下了坚实的基础.     

模型参数误差对用神经网络进行结构损伤识别的影响

通过理论推导得到了模型参数误差对损伤引起模态参数改变的贡献的表达式,用该式可指导神经网络输入参数的选择和输入向量的构造.理论分析表明,适当地构造输入向量,可以减小模型参数误差对结构损伤识别的影响.在采用BP网络和合适的输入向量后,还用数值模拟的方式对一榀六层框架的损伤识别进行了确定性研究和概率分析,结果表明,用神经网络进行结构损伤识别,受模型参数误差的影响很小,在训练神经网络时,10%的模型参数误差是可以接受的.最后,用一个两层钢框架的实验数据验证了神经网络在有模型误差时的识别能力.     

Optimum insulation for rectangular basements

The general solution of soil temperature variation is developed for a rectangular basement with a known heat flux distribution along the walls and the floor. The Interzone Temperature Profile Estimation (or ITPE) technique is applied to determine the steady-state variation of temperature within the ground. A water table at constant temperature is assumed to exist at a given depth below the soil surface. As an application of the general solution, the optimum thermal insulation distribution is determined for various basement configurations. A parametric analysis is conducted to determine the effect of basement depth and amount of heat flux required on the optimum insulation distribution along the surfaces of a rectangular basement.     

供水管网状态估计研究进展

系统地总结了供水管网状态估计的研究内容，包括参数估计、校核评估、数据（样本）设计。20年来国内外学者根据优化和统计分析理论并结合现场试验，提出了系统的理论分析和数值方法，近年来管网不确定分析理论被引入到管网校核评估和管网率定的样本数据设计中。此外还介绍了国外供水管网状态估计的精度标准。指出虽然相关理论研究有了较大进展，但应用研究相当薄弱，大型管网模型成功率定的实例还鲜有报道，今后应加强实用研究。     

Segment identification in water distribution systems

This paper presents a new method for identifying the segments that are formed after the installation and closure of isolation valves in a water distribution network. This method is able to identify segments also when one-way devices are installed in the network. Thanks to its short computing times, the method enables the analysis of real networks which always comprise a large number of nodes and pipes.

The numerical examples presented in this paper refer to two real water distribution networks. The first network is a part of a provincial network where two one-way devices are present; the second is a complex urban network without one-way devices. The method was first used to analyse the existing situation in both networks, i.e. the set of segments that are formed as a consequence of the present valve system. The method was subsequently used for the problem of the hypothetic redesign of the isolation valve system in the second urban network, i.e. the search for the optimal positions of the isolation valves in the network; in the redesign phase it provided solutions which are more cost-effective than the configuration of isolation valves currently present, the level of water service reliability being the same.     

Enhanced vulnerability assessment in karst areas by combining mapping with modeling approaches

The objective of this work is to facilitate a sustainable regional planning of water resources in karst areas by providing a conceptual framework for an integrative vulnerability assessment. A combined mapping and modeling approach is proposed, taking into account both spatial and temporal aspects of karst groundwater vulnerability. The conceptual framework comprises the delineation of recharge areas, vulnerability mapping, numerical flow and transport modeling and the integration of information into a combined vulnerability map and time series. The approach is illustrated at a field site in northwest Switzerland (Gempen plateau). The results show that the combination of vulnerability mapping and numerical modeling allows the vulnerability distribution, both in the recharge and discharge areas, to be identified, and at the same time, the time dependence of karst groundwater vulnerability to be assessed. The combined vulnerability map and time series provide a quantitative basis for drinking water management and for regional planning.     

A specific upscaling theory of rock mass parameters exhibiting spatial variability: Analytical relations and computational scheme

In this paper the representation of geological conditions in a numerical simulation model is considered. By the expression “geological conditions” we mean the 3D volume geometry of the geological formations, the spatial variability exhibited by the rock parameters inside each of these geological volumes and the necessary upscaling of the rock deformability and strength parameters that are determined in the laboratory from cores collected in the field. A specific theory is outlined of how to go from laboratory tests, geological information and field measurements and observations to the full-scale numerical or “ground model” that includes, apart from initial and boundary conditions and ground water, the rock constitutive laws and associated material parameters for use in simulation models. The term “specific” used in the title of this paper stems from the fact that other possible approaches for the same problem may be applied; i.e. empirical rock mass classification systems, explicit modeling of joints in the rock by the distinct element or finite element methods, homogenization techniques, etc. The method used to take into account the spatial variability of rock mass properties by virtue of Geostatistical Theory and 3D modeling tools is also outlined, with an example case study.     

裂隙岩体渗流溶质运移耦合离散裂隙模型数值计算方法

研究裂隙岩体渗流溶质运移问题对于岩土工程地下水污染物预测控制具有重要意义。基于离散裂隙网络模型,采用实体单元模拟基质岩块、无厚度单元模拟复杂裂隙网络,提出了裂隙岩体渗流溶质运移耦合的三维数值计算方法。针对无反应项和含反应项两种情况,通过算例分析了单裂隙中溶质迁移行为,并与精细模拟方法、解析方法的结果进行对比验证;进一步将该法应用于预测大规模裂隙岩体溶质浓度分布规律及发展趋势,并评价了主要影响因素。结果表明,该法可有效模拟裂隙网络、基质岩块中水分溶质传输行为;由于贯通裂隙网络的优势流影响,溶质羽主要受控于裂隙水的对流作用,出现了高度非均匀分布现象;通过参数敏感性分析发现,相较于岩块基质的扩散作用,裂隙开度产生的对流作用是影响浓度场分布的主控因素。在保证精度的前提下,该法可大幅减小计算量和计算时长,对于解决含复杂裂隙网络岩体渗流传质的三维数值模拟问题具有明显优势。     

镇江市主城区排水管网计算机建模方法

为了预防道路积水等城市型水灾害，基于暴雨雨水管理模型（SWMM）平台建立了镇江市主城区排水管网计算机模拟模型。结合建模实践，对排水管网计算机实用建模方法进行了探讨，可分为汇水子区域划分、参数获取、模拟情境设计、灵敏度分析及模型预校准等步骤，为后续的模型微观校准提供了有利条件。该方法对现阶段建模数据不完备地区的排水管网建模具有借鉴意义。     

红砂岩地层联络通道冻结法施工温度场分布研究

随着我国城市轨道交通技术的发展与交通需求的日益提高,国内大中型城市对地铁建设的呼声愈来愈高,而联络通道作为地铁区间的必要结构,其修建难度与区间地质关系密切,一般需要配合冻结法等地层加固技术进行施工。红砂岩地层遇水后工程性质极差,采用冻结法修建联络通道时理论及经验尚不成熟。以兰州轨道交通1号线为例,对红砂岩地层内单管冻结温度场问题进行了研究,提出了改进的单管稳态冻结温度场计算公式,并结合数值模拟结果探讨了红砂岩地层单管冻结瞬态温度场计算公式和稳态温度场计算公式的适用性。结果表明：随着时间的增加,瞬态温度场逐渐接近与其具有相同冻结锋面半径的稳态温度场,当时间取某一极大值时,两场的分布形式将一致。瞬态温度场计算公式具有较高的可靠性,因此在研究某些简单的实际工程时可采用此公式进行数值求解。稳态温度场计算公式可以看作瞬态温度场公式的特殊形式,可以配合冻结壁厚度的经验取值,实际的可靠度也较高。     

堆载预压下砂井地基固结有限元分析

采用砂井地基平面应变等效方法,结合ABAQUS软件对堆载预压下地基的侧向位移、沉降及孔压分布进行有限元模拟,并分析计算值与实测值之间的差异;计算结果能很好地预测砂井地基位移与孔压的变化,可为地基处理的设计提供参考。