Detection of Partial Blockage in Single Pipelines

A methodology is presented for the detection of partial blockages in single pipelines by the frequency response method. A steady-oscillatory flow produced by the periodic opening and closing of a valve located at the downstream end is analyzed in the frequency domain by using the transfer matrix method, and a peak pressure frequency response at the valve is developed. The comparison between the peak pressure frequency responses obtained by using the frequency response method and the method of characteristics is satisfactory. If there is a single partial blockage in a piping system, its location may be detected by the pattern and the number of peaks in the peak pressure frequency response. The size of the partial blockage may be determined from the mean peak pressure fluctuation. For two partial blockages, the effective size of the blockages can be determined from the peak pressure frequency response. Knowing the pre- and postdevelopmental frequency responses of a system with an additional partial blockage, the location and size of this additional partial blockage can be detected.     

Partial Blockage Detection in Pipelines by Frequency Response Method

A new technique is presented utilizing the frequency response for the detection of partial blockages in a pipeline. In the system frequency response, a partial blockage increases the amplitude of the pressure oscillations at even harmonics. Such an increase in amplitude has an oscillatory pattern, the frequency and amplitude of which may be used to predict the location and size of a partial blockage. In this technique, the pressure transient history at only one location is sufficient, and the history of the transient in the pipe prior to blockage is not needed, which is an advantage over a number of other available techniques, in addition to being simpler to use. It is shown that the technique successfully detects the location of a blockage in a number of simple systems with blockage size as small as 10%. The technique is verified by comparing the computed results with those computed by the method of characteristics and with measurements from simple laboratory setups. A number of practical issues and limitations for field implementations are discussed.     

Frequency Domain Analysis for Detecting Pipeline Leaks

This paper introduces leak detection methods that involve the injection of a fluid transient into the pipeline, with the resultant transient trace analyzed in the frequency domain. Two methods of leak detection using the frequency response of the pipeline are proposed. The inverse resonance method involves matching the modeled frequency responses to those observed to determine the leak parameters. The peak-sequencing method determines the region in which the leak is located by comparing the relative sizes between peaks in the frequency response diagram. It was found that a unique pattern was induced on the peaks of the frequency response for each specific location of the leak within the pipeline. The leak location can be determined by matching the observed pattern to patterns generated numerically within a lookup table. The procedure for extracting the linear frequency response diagram, including the optimum measurement position, the effect of unsteady friction, and the way in which the technique can be extended into pipeline networks, are also discussed within the paper.     

Detection of Patterns in Water Distribution Pipe Breakage Using Spatial Scan Statistics for Point Events in a Physical Network

Infrastructure systems of many U.S. cities are in poor condition, with many assets reaching the end of their service life and requiring significant capital investments. One primary requirement to optimize the allocation of investments in such systems is an effective assessment of the physical condition of assets. This paper addresses the physical condition assessment of drinking water distribution systems by analyzing pipe breakage data as the main source of evidence about the current physical condition of water distribution pipes over space. From this spatial perspective, the primary questions are whether data sets present unexpected clustering of pipe breaks, and where those break clusters are located if they do exist. This paper presents a novel approach that aims to detect and locate clusters of break points in a water distribution network. The proposed approach extends existing spatial scan statistic approaches, which are commonly used for detection of disease outbreaks in a two-dimensional spatial framework, to data collected from networked infrastructure systems. This proposed approach is described and tested in a data set that consists of 491 breaks that occurred over six years in a 160-mi water distribution network. The results presented in this paper indicate that the adapted spatial scan statistic approach applied to points in physical networks is able to detect clusters of noncompact shapes, and that these clusters present significantly higher than expected breakage rates even after accounting for pipe age and diameter. Several possible hypotheses are explored for potential causes of these clusters.     

Numerical Modeling for Hydraulic Resonance in Hydropower Systems Using Impulse Response

An effective numerical method to compute hydraulic resonance in pressurized piping of hydropower systems is presented. For this purpose, the impulse response method is used, i.e., a unit pressure impulse is introduced at the downstream waterway as an exciter. The method of characteristics is used to solve the governing equations for the hydraulic transient and to get the pressure response of the system in the time domain. The discrete Fourier transform is used to compute the frequency response of the system which gives the resonance frequencies in the hydropower plant system. To increase the accuracy of the results, unsteady friction is incorporated into the methodology. The influence of the unsteady friction, wave speed, and power on the pressure response diagram is investigated for the waterway of a multiunit hydropower plant which has been recently installed. Computed results agree very well with those obtained from the standard method of the characteristics.     

Remediation of TCE-Contaminated Groundwater in a Sandy Aquifer Using Pulsed Air Sparging: Laboratory and Numerical Studies

The objective of this study was to investigate, through laboratory and numerical investigations, the effectiveness of a pulsed air sparging system for remediation of groundwater contaminated with trichloroethylene (TCE) in a sandy aquifer. In laboratory experiments, air was pulsed into TCE source zone on a daily basis in order to remediate TCE-contaminated groundwater. Most dissolved TCE was removed at the end of experiments although its concentrations fluctuated due to the air pulsing. The measured gaseous phase TCE concentration increased whereas the aqueous phase TCE concentration decreased during air sparging pulses. Experimental data were assessed by using a numerical code STOMP (subsurface transport over multiphases) with some modification based on the TCE dissolution kinetics. The unmeasured residual TCE mass was predicted through numerical simulations. Results show that aqueous concentrations for TCE are still much higher than the maximum contaminant level in spite of successful removal of 95% of residual TCE. It may imply that it would be more appropriate to apply air sparging combined with other remediation technologies such as bioremediation for remediation of TCE-contaminated groundwater.     

Numerical Study of Flow Affected by Bendway Weirs in Victoria Bendway, the Mississippi River

It has been observed that submerged weirs in bendways realign the flow and in general improve navigation conditions. This qualitative observation has been the basis for field design. This paper presents a study of hydrodynamics in the Victoria Bendway in the Mississippi River using three-dimensional numerical simulations. A numerical model, CCHE3D, was applied and computational results were compared to three-dimensional velocity data provided by the U.S. Army Corps of Engineers with reasonable agreement. The numerical simulation results were then used to analyze helical currents due to the channel curvature and the presence of submerged weirs. The simulated flow realignment near the free surface indicates that the flow conditions in the bendway were improved by the submerged weirs, however, the effectiveness of each weir depends on its alignment, local channel morphology, and flow conditions.     

Numerical Study of the Transition Regime between the Skimming and Wake Interference Flows in a Water Flume by Using the Lattice-Model Approach

A numerical study to describe the transition regime between the skimming and wake interference flows due to the influence of an idealized bed roughness in a water flume was carried out here using the lattice model approach. The model reproduced the skimming, transition, and wake interference regimes for different aspect ratios that determine the bed roughness geometry. The simulated turbulent structures were visualized by drawing the trajectories of a large number of passive tracer particles released in the computational domain, and the results agreed with those reported by the research works. The dimensionless streamwise and vertical turbulent intensities were calculated at five test sections. The results obtained supported the visualized flow patterns permitting us to detect the presence of a shear layer developed at the top of the roughness element, whose strength varied according to the flow regime simulated.     

Delta Plots in the Study of Individual Differences: New Tools Reveal Response Inhibition Deficits in AD/HD That Are Eliminated by Methylphenidate Treatment.

The authors highlight the utility of distribution-analytical techniques in the study of individual differences and clinical disorders. Cognitive deficits associated with attention-deficit/hyperactivity disorder (AD/HD) were examined by using delta-plot analyses of performance data (reaction time and accuracy) obtained through the use of a prototypical conflict task, the Eriksen flanker task. In 20 children with AD/HD (compared with matched control participants), overall performance measures indicated a marginal performance deficit. Delta-plot analyses indicated that performance deficits associated with AD/HD involve response inhibition but not automatic response activation. In a within-subjects titration study, the response inhibition deficit was eliminated by methylphenidate treatment, but these effects were highly dose specific. The beneficial effect of methylphenidate was clarified further after correcting for inter-individual variation in sensitivity to medicine dosage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)