Development of Multiple Leakage Detection Method for a Reservoir Pipeline Valve System

The detection of multiple leakages in pipeline systems has been one of the challenging issues for the control of water loss in water distribution systems. Inverse transient analysis can be a useful principle for predicting leakage through the calibration of location and leakage quantity, based on the pressure reflection that originates from an abnormal boundary condition. In this study, an innovative leakage detection method is proposed to address unknown conditions on multiple leakage dimensions through introduction of revised leakage expressions based on a frequency domain approximation. A multiple leakage function was modified for an efficient representation of multiple abnormalities at a reservoir pipeline valve system. An iterative metaheuristic scheme (IMS) was designed to handle an optimization scheme for multiple leakages using a pressure response for a discharge impulse introduced through value manipulation. In order to address unsteady friction in hydraulic transients combined with multiple leakages, both one-dimensional and two-dimensional models were used to derive leakage expressions for turbulent and laminar flow conditions. An isolated multiple leakage function (IMLF) was proposed to exclusively encapsulate the impact of leakages and unsteady fiction. Considering uncertainties in the hydraulic transient propagation, data noise, and multiple local optima issues in large parameter calibrations, three advanced schemes were modularized to improve detectability of IMS. Several hypothetical examples were presented to show the potential of IMS, validity of three advanced schemes, and robustness in multiple leakage prediction compared to existing approaches.     

管道泄漏检测的水力瞬变全频域数学模型

输水管道泄漏孔的存在及其位置直接影响着系统压力波形的畸变和衰减特性,通过分析有、无泄漏时任意位置处的压头频域特性可使泄漏检测成为可能.在考虑非恒定摩阻影响的基础上,提出基于水力瞬变全频域数学模型的泄漏检测反问题分析方法.用拉氏频域变换处理边界条件和实测数据,并将遗传算法用于频域反问题模型的求解,在寻优速度上比传统的瞬变时域分析的方法有了较大的改善.算例表明基于水力瞬变全频域数学模型分析的管道泄漏检测是一种有效的新方法.     

Valve Maneuver Prediction in Simple and Complicated Pipeline Systems

The pressure and flow variations in pipeline systems are extremely sensitive to dynamic operations of the valves. Valve control and propagation of pressure waves along pipelines and their interactions with different pipeline elements introduce pressure transients in pipeline systems. The time series of the pressure head at any designated position depends on boundary conditions such as valve maneuver as well as geometrical and material characteristics of the pipeline system. An innovative method is proposed to calibrate the valve trajectory using pressure head records. The impedance method and particle swarm optimization were integrated with decomposition of convolution between the pressure response function and time series of the valve maneuver. To validate the applicability of this study, the developed method was tested in three hypothetical pipeline systems: a simple reservoir pipeline valve, multiple reservoir pipeline valves, and a complicated pipe network. Decomposition of the transfer function in the time domain and its convolution contributed toward improving the efficiency of the developed method. The successful calibrations of valve actions demonstrate the potential of the proposed scheme as an alternative to conventional flow meters for high-resolution flow rate evaluation.

     

供水管网泄漏检测定位方法及仪器

本文研究了城市供水管道泄漏形成多相湍射流引发应力波在管壁中传播机理，分析了泄漏引发的管道横振、纵振和园环振动，提出了一系列和波特征提取指标及其离散数据算法、研究了以泄漏信号应力波时和频域特征指标构造神经网络输入和矩阵，建立了能对管道运行状况进行分类的神经网络模型，以检测管道泄漏故障的发生。研究了抗干扰管网泄漏定位方法，分析了根据管网不同特征对定位公式进行修正以提高泄漏定位精度的方法，实验研究了这一     

考虑动态摩阻的管道泄漏水力瞬变数值模拟

为了提高管道系统泄漏的模拟和判断精度,将瞬态加速类(Brunone模型)和加权函数类(Zielke模型和Vardy模型)两类动态摩阻模型用于水力瞬变泄漏建模和模拟,并将计算结果与已有的试验数据、模拟结果进行对比分析.结果表明:与传统摩阻模型和存在简化误差的Brunone模型相比,Zielke模型和Vardy模型能更加精...     

Leak Detection in a Branched System by Inverse Transient Analysis with the Admittance Matrix Method

The diagnosis of water distribution systems by means of the inverse transient analysis requires efficient and reliable numerical models. In the network admittance matrix method (NAMM) the 1-D waterhammer governing equations are integrated in the frequency domain and organized in a laplacian matrix form. The NAMM is particularly suitable for complex systems because of this structure and can be used for the system diagnosis, including leak sizing and location. In this paper a damaged branched system is considered and the diagnosis is performed by means of the NAMM using experimental data from laboratory transient tests. Two different boundary conditions are used in the implementation of the NAMM and the leak is located and sized with a reasonable approximation. An extended numerical investigation is also presented and allows confirmation of the results for different leak locations. The use of the NAMM for the leak detection and the validation using experimental data on a branched system are the main original contributions of this work. The successful diagnosis indicates promising results for applications in more complex systems.     

Control-Oriented Impedance Matrix and Alternative Transient Control for Pipe Network Systems

In this study, a transient control method is proposed through the generation of an alternative transient in pipe network systems. A control-oriented transient analysis is performed to achieve transient control in the context of linear independence. The relationship between pressure head and discharge are incorporated into a control-oriented impedance matrix and the response function is formulated from either the discharge or pressure head impulse to either a point-scale or integrated section pressure response, or their combination. A surge control scheme is proposed by integrating a metaheuristic algorithm into the superposition platform of the response functions. Application examples demonstrate that the proposed method is a potential platform for a centralized pressure management system in a pipe network. The effectiveness of the proposed scheme in an actual system is confirmed by the method’s feasible multi-objective formulation, efficient computational cost for real-time operation, and robustness against pressure noise in commercially available sensors.

     

ANALYSIS OF FIRST TRANSIENT PRESSURE OSCILLATION FOR LEAK DETECTION IN A SINGLE PIPELINE

The leak detection is of great importance in the reliable operation and management of a pipeline system. Recently,attention is shifted to the use of the time domain or frequency domain methods based on the transient analysis. These methodssometimes require accurate pressure signals obtained during the transient period or by creating ideal conditions in testing. This paperproposes a method that does not require transient simulations over the whole or an extended period of time, but uses the first transientpressure oscillation to detect leaks. The method considers the propagation of the pressure oscillation wave created from a fast valveclosure and the reflected damp wave from the leak. A leak in the pipe gives rise to reflected waves which in turn creatediscontinuities in the observed signal at the measurement section. The timing of the reflected damp wave and the magnituderepresent the location and the size of the leak, respectively. An analytical expression is derived based on the Method OfCharacteristic (MOC) for the relationship between the leakage and the reflected magnitude. The leak detection procedure based onthe method is also given. Then the reliability of the method is tested on numerically simulated pressure signals and experimentalpressure signals with calibrated leak parameters, and the results indicate a successful application and the promising features of themethod.     

Efficient design and operation of a data acquisition system for pressurized pipeline systems.

The unsteady flow analysis of pipeline systems provides useful guidelines for implementing data acquisition components such as data filtering ranges, sensor locations and sampling frequencies. A theoretical integration among hydraulics, free vibration analysis and signal processing is proposed for a comprehensive approach aiming at enhanced design and operation of data acquisition system. Transient analysis is performed to extract flow variation by a valve modulation in a pipeline system. Frequency transformation analysis is developed to convert pressure variations between time domain and frequency domain. Free vibration analysis provides spatial distribution of impedance characteristics and pressure variation for determining optimum sensor location. A real-time filter can be designed to secure valid signals of any particular unsteady event. Hypothetical and experimental applications show that the proposed method has potentials of the leakage detection of a pipeline system as well as an efficient design of data acquisition system.     

管道系统泄漏检测的全频域法

针对长距离管道输水系统的特点,建立了适合各种边界条件的管道水击频域数学模型,并应用拉氏变换原理导出了实测离散函数的频域数学模型。在此基础上,提出完全在频域中检测管道泄漏的新方法,即管道泄漏检测的全频域法。全频域法与之前频域法的差别有两点:一是边界条件不受限制,二是泄漏检测完全在频域中完成,无需求解任何一点的傅里叶逆变换时域函数。最后通过数字算例检验了管道泄漏检测全频域法的可行性。     

水力机械模型试验台的设计研究

扼要介绍在水力机械模型试验台建设中,对试验台的主管路系统、流量率定系统、扭矩测量系统等进行的研究。开发了闸板可抽取式强迫压紧特殊阀,杜绝了管路内漏现象的发生;引进了模型水轮机叶片角度联调机构,在保证叶片角度调整精度的同时又提高了工作效率;采取了保持试验水质清洁的相关措施,节约了宝贵的水资源。该试验台通过了由中国电机工程学会和中国水力发电工程学会组织的技术鉴定,达到国际先进水平。     

基于CFD的管道漏损模拟检测与评估研究

为研究管道漏损对供水管道中水力要素变化的影响,基于计算流体动力学（CFD）方法模拟分析了有、无漏损点和不同漏损点尺寸下供水管道内部水流流动及流场变化过程。以1^#管道模拟结果为例,t=4 s时,无漏损管道拟设漏损点附近流速为0.16 m/s,压力为0.015 kPa;漏损管道漏损点附近流速峰值为0.32 m/s,压力峰值为0.068 kPa。管道整体结果表明1,管道无泄漏时,拟设漏损点附近管段内压力和流速波动较小;因泄漏,漏损管道漏损点附近管段内压力和流速出现峰值,且由沿程变化曲线可得,漏损点下游管段内压力和流速大小明显低于无漏损管道。不同模拟条件下漏损点所在管道内流速和压力具有相似的数值变化规律,但压力比流速变化更剧烈。漏损点尺寸大小与管道内流速和压力的数值变化成反比。本研究对供水管道漏损监测方案制定及监测设备布局优化具有重要的参考价值。     

Local head loss monitoring using acoustic instrumentation in partially full sewer pipes

After an increase in capital investment in UK sewers to reduce hydraulic capacity problems, the proportion of sewer flooding incidents now linked to blockages has increased. It is clear that if sewer operators are to continue to reduce flooding incidents, then better blockage management is now required. Sewer blockage formation is poorly understood; blockages are intermittent and occur in a number of circumstances. This paper reports on the development of low-cost acoustic instrumentation that can identify the location of a pipe blockage and then estimate the local head loss as a result of the presence of a blockage. A set of experiments were carried out in two full-scale laboratory pipes. The pipes' condition was altered by inserting blockages of different sizes. Acoustic data were recorded and presented in terms of the acoustic energy reflected from the partially blocked pipe. The results of this study show that the total reflected acoustic energy correlates with the measured head loss. A new empirical relation between the reflected acoustic energy and head loss due to a blockage is derived. This knowledge can then be used to estimate the reduction in flow capacity resulting from a blockage based on a single remote measurement.     

Accuracy and Sensitivity Evaluation of TFR Method for Leak Detection in Multiple-Pipeline Water Supply Systems

The transient frequency response (TFR) based pipe leak detection method has been developed and applied to water pipeline systems with different connection complexities such as branched and looped pipe networks. Previous development and preliminary applications have demonstrated the advantages of high efficiency and non-intrusion for this TFR method. Despite of the successful validations through extensive numerical applications in the literature, this type of method has not yet been examined systematically for its inherent characteristics and application accuracy under different system and flow conditions. This paper investigates the influences of the analytical approximations and assumptions originated from the method development process and the impacts of different uncertainty factors in practical application systems on the accuracy and applicability of the TFR method. The influence factors considered for the analysis contain system properties, derivation approximations and data measurement, and the pipeline systems used for the investigation include simple branched and looped multi-pipe networks. The methods of analytical analysis and numerical simulations are adopted for the investigation. The accuracy and sensitivity of the TFR method is evaluated for different factors and system conditions in this study. The results and findings are useful to understand the validity range and sensitivity of the TFR-based method, so as to better apply this efficient and non-intrusive method in practical pipeline systems.     

管道系统漏损控制技术进展

为了提高供水效率和运行管理水平,针对国内外关于供水管道系统漏损控制方面的现状,从管网故障监测技术及设备、泄漏定位模型方法、信号辨识与算法寻优、健康维护和智能管理等视角梳理了管道系统泄漏监测与漏损控制技术的进展及存在的主要问题,分析了各检测方法用于管网泄漏问题的适用性。在此基础上,从实用角度提出了管网漏损控制值得解决的关键问题和方向如下:(1)针对漏损的监测和预警,应研究面向漏损监控的管网网络组建优化布置及快速预警技术;(2)针对小泄漏的定位模型,应研究管网漏损区域辨识与基于水力反问题分析的主动检测理论和方法;(3)针对检测设备研制,应重点研发基于探地雷达、光纤传感和内窥机器人等新技术的关键设备;(4)针对管网健康维护和智能管理,应研究复杂管网独立计量区域划分方法及管网健康评价和优化维护技术。     

基于慢变流理论的管网泄漏检测模型的建立

提出一种基于慢变流理论的给水管网泄漏诊断与定位模型,即首先对管网施加随时间缓慢变化的压力激励,如果管网中存在泄漏,随着压力的不同泄漏程度也不一样,进而影响到管网中其他节点压力和管段流量等参数的变化;依据系统辨识反问题分析方法,实时监测管网监测点处的状态参数,运用贝叶斯算法对模型的预测参数——泄漏位置和泄漏量的概率值大小进行寻优,寻找模型计算值与测量值之间吻合程度最好的预测参数,得到最可能的泄漏位置与泄漏量。通过对算例管网的计算结果表明,采用该模型能够对漏失点和漏失量进行满足概率要求的准确诊断。     

泵站管路系统水力过渡过程及二次防护措施研究

为选择合适的停泵水锤二次防护措施,针对泵站管路系统的特点,运用水锤特征方程组,确定了管道瞬变流的求解方法;同时,采用Bentley Haestad Hammer软件,对重庆市松既长江提水工程子项目——金子山高位水池至上游水库提水工程的水力暂态过程进行了模拟,并对停泵水锤、被动型后保护与主动型水击预防模式引起的管道内水压变化情况进行了计算。计算结果表明:(1)在3种工况条件下,水压的峰值分别为252.80,191.80 m及174.01 m,升压比分别为1.50,1.44及1.05;(2)水泵停机时间分别为3.74,3.77 s及4.60 s,水泵均未出现反转情况;(3)被动型后保护瞬态最高水头曲线呈弓形,而主动型水击预防瞬态的最高水头曲线接近正常水头线;(4)3种工况下的阀门出口处压力波动范围分别为71.4~254.8,70.7~181.0 m及46.0~174.0 m,而且主动型的水击预防模式水泵出口的波动最为缓和。主动型水击预防可以最大幅度地降低水锤的升压峰值,是更完善的二次防护措施。     

Uniqueness,scale, and resolution issues in groundwater model parameter identification

This paper first visits uniqueness, scale, and resolution issues in groundwater flow forward modeling problems. It then makes the point that non-unique solutions to groundwater flow inverse problems arise from a lack of information necessary to make the problems well defined. Subsequently, it presents the necessary conditions for a well-defined inverse problem. They are full specifications of (1) flux boundaries and sources/sinks, and (2) heads everywhere in the domain at at least three times (one of which is t = 0), with head change everywhere at those times being nonzero for transient flow. Numerical experiments are presented to corroborate the fact that, once the necessary conditions are met, the inverse problem has a unique solution. We also demonstrate that measurement noise, instability, and sensitivity are issues related to solution techniques rather than the inverse problems themselves. In addition, we show that a mathematically well-defined inverse problem, based on an equivalent homogeneous or a layered conceptual model, may yield physically incorrect and scenario-dependent parameter values. These issues are attributed to inconsistency between the scale of the head observed and that implied by these models. Such issues can be reduced only if a sufficiently large number of observation wells are used in the equivalent homogeneous domain or each layer. With a large number of wells, we then show that increase in parameterization can lead to a higher-resolution depiction of heterogeneity if an appropriate inverse methodology is used. Furthermore, we illustrate that, using the same number of wells, a highly parameterized model in conjunction with hydraulic tomography can yield better characterization of the aquifer and minimize the scale and scenario-dependent problems. Lastly, benefits of the highly parameterized model and hydraulic tomography are tested according to their ability to improve predictions of aquifer responses induced by independent stresses not used in the inverse modeling efforts.     

反拱水垫塘单底板块位移的试验研究

该文结合溪落渡水电站，采用先进的模拟方法和量测手段，对在高水头、大流量作用下，止水完全破坏、锚筋失效等极端条件下，反拱水垫塘单底板块的位移进行了详细的试验研究，得到板块位移沿程变化的规律及其时域特性和频域特性。研究表明，反拱底板由于拱的自锁作用使其保持稳定，稳定性明显优于平底板。     

Development of numerical model for inverse modeling of confined aquifer: Application of simulated annealing method

Abstract:

The paper deals with the development of a numerical model for inverse modeling of groundwater systems based upon the simulated annealing (SA) global optimization method. Galerkin's finite element technique is developed for computing the head distribution in a confined aquifer domain. The developed numerical model is applied to the synthetic aquifer involving a set of boundary conditions, source and sink terms to compute the system parameter (transmissivity) within the chosen nine zones of the aquifer. Different data sets involving both steady and transient head values are used for these estimations. The results show that the developed model can be successfully used to obtain optimal estimates of the aquifer parameters. Based upon these information optimum model structure is also identified later from five different initial models.