Local and Global Leak Laws

The relationship between the functioning conditions of pipe systems and the leakage, or leak law, can be used at two different scales. At a local scale, i.e. for a single leak, it is derived from the classical orifice equation and, basing on experimental data, is modified to take into account all the relevant parameters it depends on (e.g., leak shape, pipe material and thickness, …). At a global scale, for a whole district or a part of a pressurized pipe system with several leaks, the same relationship is often used, basing on the assumption that the combination of local leak laws produces a similar global leak law. In this paper the effects of the spatial variation of the leak law parameters at the local scale on the leak law at a global scale are analyzed. Two leak laws derived from the orifice equation, the power law and the linear law, are considered. Results suggest that the global leak law exponent is larger than the corresponding mean local leak law exponent since it takes into account the spatial variability of the quantities affecting leakage.     

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.     

Detection of Leakage Freshwater and Friction Factor Calibration in Drinking Networks Using Central Force Optimization

Inverse Transient Analysis (ITA) is a powerful approach for leak detection and calibration of friction factors in pressurized pipes. Through this method, a transient flow is initiated and pressures are measured somewhere in the system. Then, a nonlinear programming (NLP) problem with a least-squares criterion objective function is developed to minimize discrepancies between the measured and calculated pressures at measurement sites. Solving the raised NLP results in the problem’s unknowns being leakage specifications and pipe friction factors. For this purpose, various optimization techniques may be utilized. This issue is a major challenge for ITA-based methods. The present work aims at applying the new method of Central Force Optimization (CFO) to the problem of ITA. CFO is a deterministic metaheuristic inspired by gravitational kinematics in which small objects in space are dragged by bigger ones. Herein, the concept and main structure of CFO are represented as well as of CFO. A reference pipe-network is considered to be solved using the ITA equipped with CFO. The results are then discussed compared to the previous works. It is concluded that CFO is easy to implement, computationally efficient and has a remarkable performance in solving leak detection problem.     

Sediment management and flow patterns at river bend due to triangular vanes attached to the bank

Triangular vanes are hydraulic structures used for bank protection and habitat restoration for fish and other aquatic organisms. There are limitations on the design criteria for this newly-introduced structure; therefore, the main goal of this paper is to present test results carried out on different alternatives of multiple vanes with different spaces between the vanes under different hydraulic conditions in a 90-degree mild flume bend. In addition, 3D components of flow velocity were measured in tests with and without an installed single vane. The triangular vanes create a counterclockwise secondary flow cell near the outer bank, which counteracts the clockwise main secondary flow cell in the bend for a distance of about 5le (le is the vane's effective length) downstream of the vane's position. With multiple vanes in place, the thalweg was found to be shifted toward the flume midway from the outer bank. Moreover, by increasing the space between the triangular vanes, the scour around the vane's tip and its development to the outer bank increased. Therefore, it is concluded that triangular vanes perform best when they are spaced at 5le or less.     

Selecting the Best Flood Flow Frequency Model Using Multi-Criteria Group Decision-Making

Several criteria should be considered when selecting a probability distribution to describe hydrological data. This study examines how multiple criteria can be combined to make the best selection. Selection becomes more difficult and subjective when more than two criteria are used to determine the best distribution. Under these conditions, multi-criteria decision-making is necessary. In this study, 12 distributions were tested and compared for flood frequency analysis based on five selection criteria: root mean square error, Kolmogorov-Smirnov test statistic, relative average bias, modified Anderson-Darling test, and deviation in skewness and kurtosis. The comparisons are made using a multi-criteria group decision-making (MCGDM) based on ordered weighted averaging (OWA). Two preemptive goal programming models based on variance and entropy methods for a predetermined level of optimism by a group of decision-makers, determined the weight of the OWA operator. The model was applied to a case study of Mahabad River, a major river flowing into Lake Urmia in northwestern Iran. A sensitivity analysis of the results of MCGDM was done by changing the degree of optimism of the decision-makers. The results of sensitivity analysis showed the dependence of the rankings to the optimism degrees of the decision-makers. The 3-parameter Weibull (WBL3) and Pearson type 3 (PE3) distributions had the best results for Mahabad River flood data. A Monte Carlo simulation was conducted to test the ability of the models. It was concluded from the findings of the simulation that the PE3 distribution is the most appropriate for short sample sizes, while WBL3 is preferable for larger sample sizes.     

急流弯道优化设计方法的具体试验研究

泄水建筑物由于受到地形及其他因素的限制,常需在泄槽段设置弯道。由于弯道水流本身所具有的特点,如不采取工程措施加以改善,将威胁建筑物的安全运行。目前急流弯道优化设计方法甚多,但各种方法有其各自的优点,本文目的在于通过模型试验对几种优化设计方法进行研究,以便为各工程实际选择一种效果显著、经济可行的方法提供依据。     

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.     

Helminth ova control in sludge: a review.

Sludge reuse for agricultural production or soil reclamation is a common practice in several countries, but it entails risks if not properly performed. One such risk is the dissemination of helminthiases diseases. As a consequence, international criteria and national standards set values to limit their content in biosolids. However, little information is available on how to inactivate helminth ova from sludge, particularly when a high content is involved as is the case in the developing world. Moreover, treatment criteria are based on a limited number of studies dealing with local characteristics that, when applied to the conditions in developing countries, produce poor results. This is because design criteria were developed for Ascaris (a kind of helminth) while sludge contains a variety of genera. In addition, much information on helminth ova was produced a long time ago using inaccurate analytical techniques. This paper summarizes research and recent technical information from the literature concerning: (a) the general characteristics of helminth ova; (b) the common helminth ova genera found in sludge; (c) the main removal and inactivation mechanisms, (d) the processes that have proven effective in practical conditions at inactivating helminth ova; and (e) analytical techniques used to enumerate these pathogens.     

堤防漏洞查堵演示试验技术研究

堤防漏洞险情为较高水位情况下堤防背坡出现贯通堤身的流水孔洞，是堤防八大险情之一。漏洞险情发展快、危害大、抢堵难度大。为提高防汛专业队伍查堵漏洞的技术水平，封丘县黄河河务局于１９９７年７月１８晶，在曹岗险工０－１号坝之间，进行了堤防漏洞查堵演示试验。演示的目的是模拟不同条件下出现的各种漏洞险情，试验条件探找洞口和抢堵漏洞的方法，研究各种抢堵方法的可操作性和适用条件，提高抢险堵漏洞的技术水平。     

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.     

Time and Energy Savings in Leak Detection in WSN-Based Water Pipelines: A Novel Parametric Optimization-Based Approach

This paper presents a novel optimization algorithm for monitoring a complex water pipeline using Wireless Sensor Networks (WSN), in order to solve the trade-off between a timely and accurate detection of a leak, and an efficient utilization of the energy at the WSN’s nodes aimed at prolonging the WSN’s lifetime. The scheme relies on using vibration sensors of different sensitivities to detect vibrations due to a leak, and on exploiting duty-cycling, hierarchical adaptive sampling and wavelet-based signal compression, in order to reduce sensing, computation and communication energies. Given the constraints of a maximum allowable sensor energy, a limited time to detect a leak after it occurs, and an acceptable percentage of signal distortion due to compression, a new optimization-based backtracking learning algorithm is developed here that solves for the values of various monitoring parameters such that it satisfies all the given constraints. Developing such an optimization algorithm has also required performing a sensitivity analysis, i.e. investigating the effect of changing the key monitoring parameters on the performance of leak detection and energy consumption. Simulation results for various cases successfully demonstrate the effectiveness of the algorithm while supporting the prediction of the sensitivity analysis.

     

Experimental Evidence of Leaks in Elastic Pipes

Several studies have been carried out in recent decades to establish a relationship between total head and leaks. In literature, the leakage governing equations have been analysed in light of pipe materials, water head, leak dimension or shape. Most of these contributions questioned the classical Torricelli equation, demonstrating through experimental evidence that the classical orifice law can give unsatisfactory results. Nevertheless, starting from the Torricelli equation, other exponential or linear governing equations have been proposed as mathematical models able to reproduce the leakages in water distribution systems (WDSs). To investigate the validity of the proposed governing equations, an experimental campaign was carried out by means of a water distribution network composed of approximately 500 m of polyethylene pipes. The experiments were designed to investigate the effects of leak area and pipe rigidity on discharge. Furthermore, the effect of leak size enlargement with water head was analysed. Finally, the proposed research contributes to the population of a database for estimating the coefficients of head-discharge relationships.     

Random Bagging Classifier and Shuffled Frog Leaping Based Optimal Sensor Placement for Leakage Detection in WDS

Water Resources Management - Water Distribution Systems (WDS) are the large scale systems that demand design of enhanced leak detection and isolation techniques to prevent from water waste....     

A note on acoustic measurements of turbulence,suspended sediment,and bed forms in mobile-bed experiments

Mobile-bed laboratory measurements allow observation of interactions between turbulent sediment-laden flows and irregular, non-stationary bed topography. Water in mobile-bed experiments is typically clouded by suspended particles, complicating the use of optical and laser based measurement techniques. In such conditions, acoustic techniques can be used to measure turbulence, suspended sediment transport, and bed topography; however, these procedures also have unique challenges. Here, the effect of suspended particles on acoustic Doppler turbulence measurement, the effect of particle size on acoustic measurement of suspended-sediments, and a method for statistically describing bed topography (measured acoustically or otherwise) are addressed. It is found that suspended particles have a small effect on Reynolds stresses measured with an acoustic Doppler velocimeter and that those effects could be minimized by excluding data collected with the highest and lowest acoustic amplitudes. The effect of particle size on acoustic backscatter amplitude is most strongly pronounced for particles smaller than 0.3 mm. Semivariogram analysis is shown to be a viable method for analyzing complex bed topography produced by mobile-bed experiments.     

Estimation of Monthly Mean Reference Evapotranspiration in Turkey

Monthly mean reference evapotranspiration (ET ₀ ) is estimated using adaptive network based fuzzy inference system (ANFIS) and artificial neural network (ANN) models. Various combinations of long-term average monthly climatic data of wind speed, air temperature, relative humidity, and solar radiation, recorded at stations in Turkey, are used as inputs to the ANFIS and ANN models so as to calculate ET ₀ given by the FAO-56 PM (Penman-Monteith) equation. First, a comparison is made among the estimates provided by the ANFIS and ANN models and those by the empirical methods of Hargreaves and Ritchie. Next, the empirical models are calibrated using the ET ₀ values given by FAO-56 PM, and the estimates by the ANFIS and ANN techniques are compared with those of the calibrated models. Mean square error, mean absolute error, and determination coefficient statistics are used as comparison criteria for evaluation of performances of all the models considered. Based on these evaluations, it is found that the ANFIS and ANN schemes can be employed successfully in modeling the monthly mean ET ₀ , because both approaches yield better estimates than the classical methods, and yet ANFIS being slightly more successful than ANN.     

Comparison of hydrolytic enzyme systems in pure culture and activated sludge under different electron acceptor conditions

Enzymatic hydrolysis under different electron acceptor conditions in nutrient removal activated sludge treatment processes is a weak link in the Activated Sludge Model no. 2 (Henze et al., 1995). An experimental study was undertaken to gain insight into the hydrolysis process with specific focus on hydrolysis kinetics and rates under different electron acceptor conditions. Two pure cultures, Bacillus amyloliquefaciens (Gram positive) and Pseudomonas saccharophila (Gram negative) were chosen for the study. In addition, activated sludge grown in an anaerobic-aerobic system was tested for enzymatic activity using starch as the model substrate. The hydrolytic enzymes were found to be released into the bulk in pure cultures whereas the enzyme activity was found to be mainly associated with the cell surfaces in activated sludge. Further, it was observed that the development of the hydrolytic enzyme system in Bacillus amyloliquefaciens and P. saccharophila is strongly suppressed under anoxic and anaerobic conditions. However, the effect of anaerobic and aerobic incubation on hydrolytic enzyme activity in activated sludge was found to be small. Starch hydrolysis kinetic data from batch experiments with activated sludge followed substrate saturation kinetics that were linear with biomass concentration. Finally, the similar hydrolytic enzyme activities observed under anaerobic and aerobic phases of a sequencing batch reactor are explained by considering the aspects of enzyme location and enzyme system development under aerobic and anaerobic phases. It is proposed that the floc bound enzymes are recycled in a single sludge system so that an equilibrium exists between enzyme loss and synthesis at steady state.     

土地利用变化下的水文响应及其可检测性分析

以涪江桥流域为研究区域,采用SWAT模型模拟流域水文过程,将相同水文气象条件下1985和1995年2个时期土地利用情景的SWAT模型模拟结果与土地利用空间转化图相结合,分析土地利用变化引起的水文要素变化及其可检测性问题。结果表明:1985—1995年间涪江桥流域发生较为剧烈的土地利用变化,但并未检测到足够显著的水文要素变化;不同土地利用类型水文效应的相似性、不同土地利用类型水文效应差异性以及统计中和效应和统计均化效应是导致土地利用变化引起的水文要素变化难以检测的主要原因。在此基础上,提出了水文动态响应度指标,来消除统计中和效应。该指标可以在一定程度上帮助研究者了解研究区特定水文要素变化的相对剧烈程度。研究结果可为土地利用总体规划和流域水资源保护与合理配置提供参考。     

Energy Production in Water Distribution Networks: A PAT Design Strategy

Pump operating as turbine (PAT) is an effective source of reducing the equipment cost in small hydropower plants. However, the manufacturers provide poor information on the PAT performance thus representing a limit for its wider diffusion. Additional implementation difficulties arise under variable operating conditions, characteristic of water distribution networks (WDNs). WDNs allow to obtain widespread and globally significant amount of produced energy by exploiting the head drop due to the network pressure control strategy for leak reductions. Thus a design procedure is proposed that couples a parallel hydraulic circuit with an overall plant efficiency criteria for the market pump selection within a WDN. The proposed design method allows to identify the performance curves of the PAT that maximizes the produced energy for an assigned flow and pressure-head distribution pattern. Finally, computational fluid dynamics (CFD) is shown as a suitable alternative for performance curve assessment covering the limited number of experimental data.     

TEMPORAL AND SPATIAL DISCRETIZATION ON QUASI-3-D GROUNDWATER FINITE ELEMENT MODELLING TO AVOID SPURIOUS OSCILLATION

In this article, the finite element solution of quasi-three-dimensional (quasi-3-D) groundwater flow was mathematically analyzed. The research shows that the spurious oscillation solution to the Finite Element Model (FEM) is the results choosing the small time step ?t or the large element size L and using the non-diagonal storage matrix. The mechanism for this phenomenon is explained by the negative weighting factor of implicit part in the discretized equations. To avoid spurious oscillation solution, the criteria on the selection of ?t and L for quasi-3-D groundwater flow simulations were identified. An application example of quasi-3-D groundwater flow simulation was presented to verify the criteria. The results indicate that temporal discretization scale has significant impact on the spurious oscillations in the finite-element solutions, and the spurious oscillations can be avoided in solving practical quasi-3-D groundwater flow problems if the criteria are satisfied.     

特高土石坝建设与安全保障的关键问题及对策

随着我国水资源利用进程的推进,一批建设条件和运行环境更加复杂、坝高200 m以上的特高土石坝正在建设或即将开工建设,这些高坝大库的顺利建设与长期安全事关国家经济社会发展和公共安全。分析了复杂条件下特高土石坝建设和长期安全保障面临的理论与技术挑战以及需要解决的关键科学与技术问题,提出了以下重点研究内容:通过筑坝粗粒料和坝体结构的多尺度试验、已建高土石坝运行性状反馈分析、先进数值模拟方法的发展等手段,分别从材料和结构层面,揭示特高土石坝粗粒料力学性质尺度效应、接触面变形与破坏机制、防渗系统服役性能演化规律,建立其长期安全评价理论体系,显著提升特高土石坝变形与渗流安全预测精度;通过新结构、新材料、新设备、新标准的研发,解决复杂河谷条件、恶劣气候条件下坝体结构和防渗系统变形协调与渗流安全问题,形成复杂条件下特高土石坝灾变防控技术体系;基于我国大型水库在线安全监测平台,通过引入先进的卫星遥感技术、制订安全评价标准等,构建特高土石坝安全实时监控与风险预警平台,实现对特高土石坝安全的实时监控、风险预警、信息发布和应急处置指导。从而为进一步提升我国特高土石坝建设水平和安全保障能力提供理论与技术支撑。