1,720,975 research outputs found
Mechanism of interaction of pressure waves at a discrete partial blockage
No full textThis paper analyses the mechanism of interaction between an incident pressure wave and blockages of different geometrical characteristics (i.e., a butterfly and a ball valves, two short stretches of pipe with a reduced diameter, and a device simulating a longitudinal body blockage) by means of laboratory and numerical tests. Experiments have shown that the mechanism of interaction with pressure waves is influenced by their path through the device: sinuous because of the device body for partially closed in-line valves (type I mechanism), and straight for the small bore pipe devices (type II mechanism). Type I mechanism is characterized by a rise followed by an almost constant value whereas in type II one a drop occurs after the rise. To complete the investigation the effect of the pre-transient condition is discussed
A Nelder–Mead algorithm-based inverse transient analysis for leak detection and sizing in a single pipe
No full textHydraulic Characterization of PVC-O Pipes by Means of Transient Tests
No full textAbstractMolecularly oriented PVC (known as PVC-O) was developed as an improvement to conventional unplasticized PVC (or PVC-u). For a given nominal pressure, the biaxial orientation of the pipe material allows to double the tensile strength and increase flexibil- ity and resistance to cyclic fatigue, with a reduction in weight. Although the PVC-O pipes are produced and used since late 80s, the behavior of such pipes during transients is not well characterized in literature. In the paper we present the results of transient tests carried out on a PN16 DN110 pipe and generated by maneuvering an automatically controlled butterfly valve. The experimental setup has been installed at the Water Engineering Laboratory of the University of Perugia, Italy. Both time domain and frequency domain analyses are performed. The pressure wave speed is evaluated experimentally by means of pressure measurements. Infor- mation deriving from strain gauges is used to verify and characterize the actual viscoelastic behavior of PVC-O pipes
Leak-Induced Pressure Decay During Transients in Viscoelastic Pipes. Preliminary Results
No full textAbstractIn this paper, the dynamics of pressure peaks in a single viscoelastic pipe with a leak (leaky pipe) is examined by means of laboratory and numerical experiments. Experimental tests are the necessary premise to a reliable calibration of a 1-D numerical model which allows to investigate in detail a wide range of both geometrical and flow conditions by taking into account not only the leak but also energy dissipation due to viscoelasticity and unsteady friction. In the analysis, the decay of the maximum values of the pressure is assumed as a representative characteristic of the dynamics of the examined transients in the long term. The numerical campaign has pointed out the characteristic quantities affecting the investigated phenomenon as well as the structure of the pressure decay law
Risk based sensor placement methods for burst/leak detection in water distribution systems
Full text linkThis is the author accepted manuscript. The final version is available from IWA Publishing via the DOI in this record.The optimal placement of sensors in water distribution systems for burst/leak detection is usually formulated as an optimization problem. In this study three different risk-based functions are used to drive optimal location of a given number of sensors in water distribution network. A simple function based on likelihood of leak non-detection is compared with two other risk-based functions, where impact and exposure are combined with the leak detection likelihood. The impact is considered proportional to the demand water volume while the exposure is related to the importance of the connections and it is evaluated on social, economic or safety considerations. The methods are applied to a district metered area of the Harrogate network by means of a modified EPANET model, to take into account the pressure driven functioning conditions of the system. The results show that the exposure can lead to a different sensor location ranking with respect to other used criteria and hence the proposed methodology can represent a useful tool for the water system managers to distribute the sensors in the network, complying to hydraulic, social and economical requirements.The authors are grateful for the Erasmus funding which enabled the first author to do most of this work at the University of Exeter in the UK
Performance Assessment of Pneumatic-Driven Automatic Valves to Improve Pipeline Fault Detection Procedure by Fast Transient Tests
No full textThe use of fast transients for fault detection in long transmission networks makes the generation of controlled transients crucial. In order to maximise the information that can be extracted from the measured pressure time history (pressure signal), the transients must meet certain requirements. In particular, the manoeuvre that generates the transient must be fast and repeatable, and must produce a pressure wave that is as sharp as possible, without spurious pressure oscillations. This implies the use of small-diameter valves and often pneumatically operated automatic valves. In the present work, experimental transient tests are carried out at the Water Engineering Laboratory (WEL) of the University of Perugia using a butterfly valve and a ball pneumatic-driven valve to generate pressure waves in a pressurised copper pipe. A camera is used to monitor the valve displacement, while the pressure is measured by a pressure transducer close to the downstream end of the pipe where the pneumatic valve is installed. The experimental data are analysed to characterise the valve performance and to compare the two geometries in terms of valve closing dynamics, the sharpness of the generated pressure wave and the stability of the pressure time history. The present work demonstrates how the proposed approach can be very effective in easily characterising the transient dynamics
Swinging pressure reducing valve in a real water distribution network: Where is the catch?
No full textTo reduce leakage in water distribution networks, several strategies have been developed, each addressing different aspects of the problem. Alongside advanced leak detection technologies, pressure control has proven to be one of the most powerful and widely implemented strategies to reduce leakage. In this perspective, a key technology in pressure management is the use of pressure reducing valves (PRVs). This paper presents field measurements showing significant instability (swing) of a PRV installed in a real pressure management area in Trieste (Italy). Such instability is characterized by very frequent and significant pressure variations. The various factors influencing this feature are pointed out, finding the catch of the problem and suggesting effective solutions
Pump operations-induced transients in water distribution systems. Laboratory experiments
No full textPump startup and shutdown induce transients in pressurized water distribution networks (WDNs) that can cause significant pressure variations, posing a risk to the system's integrity, and potentially leading to fatigue failures. This paper presents laboratory experiments designed to study pump-induced transients in a full-scale WDN at the Water Engineering Laboratory of the University of Perugia, Italy. The experimental setup includes a network of high-density polyethylene pipelines arranged in two loops, supplied by pumps set in series. Various pump startup and shutdown scenarios were tested, and the resulting transient pressures were acquired at multiple locations in the network. Both short- and long-period analyses of the experimental pressure signals identify the most vulnerable sections of the network as those either closest to the pump station or located in smaller-diameter pipelines, where wave interactions and trapped surges amplify pressure fluctuations. Particularly under low-demand (e.g., nighttime-like) conditions, these transient waves intensify. The findings also reveal how changes in network configuration and boundary conditions can significantly influence transient dissipation rates. The results provide valuable insights for water utility managers, aiding in the identification of critical network portions and the optimization of pump operations to preserve system integrity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
