جستجوی مقالات مرتبط با کلیدواژه "نشت یابی" در نشریات گروه "آب و خاک"

Conventional leak detection methods are costly and time-consuming, so attention has recently been drawn to methods that detect leakage by network modeling comprehensively.

In these methods, the difference between the measured pressure and flow rate and those obtained by the model is minimized as a fitness function by calibrating the network and adjusting the nodal demands. It has been established by analysis that the fitness function in itself cannot be a good guide to achieving the minimum point. This drawback was solved by using the ACO method. In addition to the fitness, this method employs a parameter called heuristic guidance to improve its capabilities.

This research compared three ACO-based optimization methods. The first was ACO with fixed heuristic guidance already introduced in the literature. In the second method, the heuristic guidance varies by the values of the observed pressures and pressure decline versus the no-leak state. The third is studied and compared by integrating SSEM and ACO models. These methods were investigated on a network derived from the literature and the Birjand network.

The results revealed that the methods proposed here achieved more precise results in a shorter time and with fewer iterations.

Recently, calibration based methods are developed for leak detection in water distribution networks (WDN). These methods are collected the pressures and flows data of a real network and try to regulate the demands in hydraulic network model to match the model results with observations. Therefore, in addition of hydraulic analysis, an optimization algorithm is needed. In this study, a new population based optimization method is presented. In this method, the network first is zoned to some regions. First generation are guessed for appearance loss and leakage in each zone and answers fitness are calculated. Moreover, a new factor named minor fitness, developing in this research, is computed for each zone in all answers. A small minor fitness in a zone, predicts the correct value of leakage. With combination of the results of best answers, in each generation, a range is calculated for the next generation selection. This range become narrower in consecutive generations and the correct answer is found. The proposed method is investigated on a real network with hypothetical leakages. The results obtained in model are evaluated with the assumed value, as well as, WaterGEMS model results.  The results show the capability of the proposed optimization method in detection of the both location and the value of leakage. Comparing this method with Darwin calibrator show more accuracy, convergence and speed of the proposed method. The fitness in the present study method and WaterGEMS calibration are 0.654 and 0.817, respectively.

Water resources management is one of the most important issues that are considered by experts in this field due to the reduction of rainfall and the reduction of groundwater levels. In this study, to reduce pipe fractures and water loss in Salehabad city (Comparison of water production and customer consumption data showed that there is more than 60 percent water loss in this network) field studies, pressure gauges, leak detection, and hydraulic analysis were performed by combining AutoCAD, WaterGEMS and GIS software. Points of the water distribution network that had more than 50 mH2o pressure were identified and then by field studies and using the method of closing the gate valves as a step by step, 6 points were identified as high-risk points of leakage. Therefore, with the check of the areas by the leak detector, 3 cases of pipe fractures were found and the remeasurement showed that the repair of these pipe fractures had reduced water loss by 20 percent. Depending on the urban texture and topography of the area, it was suggested to reduce the network pressure to 16 to 30 mH2o by installing a pressure relief valve in critical points of the network.

In addition to wasting water and energy, leaks in water distribution networks also cause social and environmental problems. So it is important to try to save as much as possible. In leaks made by meta-heuristic methods, the decision variables are leak node number and flow leakage. In this study, a method is presented with the combination of inverse solution of flow equations and meta-heuristic algorithm. In the proposed method, only the leakage node number is considered as the decision variable in the Harmony search method, and the leakage amount is calculated using the inverse solution of continuity and energy equations. In addition to a number of measurements for the objective function of the meta-heuristic algorithm, it is necessary to measure pressure nodes and discharge pipes as many as leakage nodes for the hydraulic model. The results in the two hypothetical networks show that this method determines and calculates the position and amount of leaks with high accuracy, even if the leakage amount is small. If there is an error in measuring the node pressure, the position and amount of leaks are calculated accurately by increasing the nodes of the objective function.

Introduction  When a sudden pressure surge is induced in a pipe system, discontinuities like leaks, changes of pipe diameter or material, tee-junctions, local head losses or air pockets, introduce changes in the hydraulic transient event propagation. A leak creates a pressure drop; friction increases pressure damping; a dead-end or a closed-valve reflects totally an incident wave; an air bubble creates a pressure drop followed by a pressure increase.     The detection of these signals allows their identification and location. The information carried in the transient pressure signal can be used to detect, locate and size leaks, and, eventually, to distinguish these from other features existing in the pipeline.   Methodology Physical model     The purpose of this study was to find the location and size of leakage in polyethylene transfer pipes using transient flow. Therefore, a laboratory model was developed for this purpose at the Hydraulic Lab of the Faculty of Engineering Sciences of Shahid Chamran University of Ahvaz.