On the use of power reflection ratio and phase change to determine the geometry of a blockage in a pipe

Abstract

Article:Duan, W., Kirby, R., Prisutova, J. et al.(1 more author) (2015) On the use of power reflection ratio and phase change to determine the geometry of a blockage in a pipe. Applied Acoustics, https://doi.org/10.1016/j.apacoust.2014.07.002 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. 1On the use of power reflection ratio and phase change to determine the geometry of a blockage in a pipe the echo from the blockage. This presents a fast and efficient way of determining the presence of a blockage and this method is now being used, for example, to probe the integrity of sewer systems. In this article a method is presented for obtaining both the length and the equivalent cross-sectional area of a blockage using only a single microphone to capture the incident and reflected pulse. The method presented uses the change in phase between the incident and reflected acoustic signals caused by a blockage, as well as the difference in the amplitude of each pulse, to generate two independent equations from which the area ratio and the length of the blockage may be recovered. This requires measurements to be carried out in the plane wave region of the pipe, however it is shown that through appropriate processing of each signal in the frequency domain the area ratio and length of a relatively large number of blockages can be successfully recovered.

Bragg-Type Resonance in Blocked Pipe System and Its Effect on the Eigenfrequency Shift

“…9indicates that if the blockage length is a multiple of the half wavelength, then the injected wave is totally transmitted through the blockage. For example, Duan et al (2015) used a blockage detection technique that relies on measuring the reflection coefficient. In the experimental work, Duan et al (2015) varied the central frequency of the generated wave to determine which wave frequencies reflect maximally, which results in maximum reflection (and accuracy) according to the Bragg resonance condition.…”

“…For example, Duan et al (2015) used a blockage detection technique that relies on measuring the reflection coefficient. In the experimental work, Duan et al (2015) varied the central frequency of the generated wave to determine which wave frequencies reflect maximally, which results in maximum reflection (and accuracy) according to the Bragg resonance condition. In the experiments, Duan et al (2015) found that for blockage lengths equal to odd integer multiples of the quarter wavelength, the power reflection ratio becomes maximum.…”

“…In the experimental work, Duan et al (2015) varied the central frequency of the generated wave to determine which wave frequencies reflect maximally, which results in maximum reflection (and accuracy) according to the Bragg resonance condition. In the experiments, Duan et al (2015) found that for blockage lengths equal to odd integer multiples of the quarter wavelength, the power reflection ratio becomes maximum. Again, this is precisely the condition of Bragg resonance frequency of maximum reflection [Eq.…”

“…It will be seen that these insights are useful in the design of effective probing signals. For example, Duan et al (2015) swept the frequency bandwidth (FBW) of the probing signal to obtain the highest reflection coefficient that leads to accurate detectability of the blockage. It will be shown heuristically, analytically, and theoretically that this mechanism is directly related to Bragg resonance effects (Bragg and Bragg 1913).…”

Eigenfrequency Shift Mechanism due to an Interior Blockage in a Pipe

“…This technique is used to image the human vocal tract system. More recently, the technique elicited considerable interest on the part of water supply researchers (Duan et al 2011(Duan et al , 2013Lee et al 2013;) and its utility was extended to other fields of application (Duan et al 2015).…”