Numerical and Experimental Study on Propagation Attenuation of Leakage Vibration Acceleration Signal of the Buried Water Pipe
Jun Liu
Jawwad Latif
Round 1
Reviewer 1 Report (Previous Reviewer 1)
The authors have adopted the comment from the reviewers in my option. Therefore, I suggest acceptance for publication.
Author Response
We appreciate your valuable comments and recognition of our work.
Reviewer 2 Report (Previous Reviewer 3)
The author has carefully addressed the points.
Author Response
We appreciate your valuable comments and recognition of our work.
Reviewer 3 Report (New Reviewer)
This paper by Yang et al. attempts to develop a method to detect leakage. The strength of the paper is that it is comprehensive and the numerical simulations are validated with experiments. However, the weakness of the paper is in describing the theory in section 3.1 and 3.2,
In section 3.1:
a. In equation (1), S is stated to be surface force which is not correct. It should be stress. Also, if author states its a surface force. derivatives are not defined on the surface. Please correct the equation.
b. When mentioning the strain, please limit what all strains were used in the manuscript.
The details in section 3.2 is not clear. It is better to explain boundary conditions in detail. For Z=1.2 m. why 2 displacement constraints are used Eq. (4) and Eq. (5). Also, how can both Dirichlet and Neumann boundary conditions be applied at same location?
In section 3.3,
a. It is stated mesh size should not be less than 28 mm and then in next sentence it is mentioned maximum unit size of pipe is 25 mm. Please clarify the statements.
b. In paragraph 4, the calculation time is set to [......]. Its not clear why 3 values are written also what is the unit?
Other minor comments
1. Figure 11, shows acceleration vs time however the captions states Test group velocity calculation
2. How Eq. (9) is related to Table 3?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This study combines test and numerical simulation methods to study the influence of pipeline leakage signal on distance and pipe covering soil on signal transmission and its distribution. It is innovative and has theoretical and practical significance. The research outcome is suitable for the audience of the journal. But, the following concerns should be addressed before accepted:
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper addresses the topic of computing the propagation parameters of elastic waves generated by a leaking hole in a water transportation pipeline.
The problem is not new, and it has been presented in several references (see below, from an internal report A of 2014: more studies has been added in the recent years). Also the characterization of the source (noise from a leaking hole) has an important literature, whose main contributor is Michael James Lighthill.
The paper shows the results of a field experiment, and claims a comparison with a COMSOL simulation.
The following is a partial list of reasons for suggesting of the document:
- It is not clear up to the description of the experimental setup what kind of sensors are used and where they are positioned (hydrophones in contact with the fuid, or accelerometers on the pipe shell, or ...)
- The spectral analysis is very "rough" (only 3 bands up to 25000Hz) and misleading: I would expect an exponential decay along the frequency for increasing distance.
- The derivation of the wave velocity is performed by a visual selection of corresponding peaks (???) in the raw data of two sensors: the result is completely unreliable. The authors should use, for example, a cosscorrrelation analysis, that is already mentioned in the text.
- English form is very poor
- there is no novelty in the presented material
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From report A
In the case of gas-filled pipelines, the pipe can usually be considered a rigid medium and the simple wide-tube approximation which describes the fluid-borne wave propagation (Blackstock [1]) is sufficient for most practical application, as claimed by Stecki & Davis [2]; in the case of liquids, the compressibility of the fluid is comparable to the compressibility of the pipe material and therefore the properties of the shell are important and possibly even the properties of the external medium.
To this end, an interesting model is proposed by Pinnington and Briscoe [3] and extended by Muggleton [4], which accounts for pipe elasticity, and surrounding solid medium effects, but neglects fluid viscosity. In particular these authors show the large contribution to wave attenuation due to the outward radiation of both pressure and shear waves. The advantage of these models is their analytic form but their validity falls in proximity of the ring frequency.
In fact, in order to obtain solutions for all frequencies and all propagation modes, a more complex matrix method is needed, which was well described in Gazis [5]. More recently the matrix method was employed among others by Rama Rao and Vandiver [6] for propagation in boreholes, Sinha et al. [7] and Plona at al. [8] for fluid loaded pipes filled with inviscid fluid.
This approach has been generalized to any sequence of cylindrical elastic layers as the Global Matrix Method (Lowe [9]) and implemented in the Disperse software by Imperial College (Pavlakovic [10]); fluid layers are then treated as equivalent elastic solid layers introducing the fluid viscosity by means of a fictitious shear wave (Aristegui et al. [11], Long et al. [12], Vogt at al. [13], Ma et al. [14]).
Elvira-Segura [15] also used a matrix method to couple an internal viscous fluid with an external solid layer surrounded by vacuum, this model was recently used and extended to viscous shells by Baik [16].
[1] Blackstock, D. T., Fundamentals of physical acoustics, John Wiley & Sons, Inc., 2000.
[2] Stecki, J. S, & Davis, D. C., Fluid transmission lines: distributed parameter models, Proceedings of the Institution of Mechanical Engineers, 1986.
[3] Pinnington, R., & Briscoe, A., Externally applied sensor for axisymmetric waves in a fluid filled pipe, Journal of Sound and Vibration 173, 503–516. 1994.
[4] Muggleton, J., Brennan, M., & Pinnington, R., Wavenumber prediction of waves in buried pipes for water leak detection, Journal of Sound and Vibration 249, 2002
[5] Gazis, D. C., Three-Dimensional Investigation of the Propagation of Waves in Hollow Circular Cylinders, I. Analytical Foundation, and II. Numerical Results, J. Acoust. Soc. Am. 31, 568-577, 1959.
[6] Rama Rao, V. N. and Vandiver, J. K., Acoustics of fluid-filled boreholes with pipe: Guided propagation and radiation, J. Acoust. Soc. Am. 105, 3057–3066, 1999.
[7] Sinha, B. K., Plona, T. J., Kostek, S., & Chang, S., Axisymmetric wave propagation in fluid-loaded cylindrical shells. I. Theory, J. Acoust. Soc. Am. 92 (2), 1132–1143, 1992.
[8] Plona, T. J., Sinha, B. K., Kostek, S. & Chang, S. K., Axisymmetric wave propagation in fluid-loaded cylindrical shells. II. Theory versus experiment, J. Acoust. Soc. Am. 92, 1144-1155, 1992.
[9] Lowe, M. J. S., Matrix Techniques for ModelingUltrasonic Waves in Multilayered Media, IEEE Transactions Ultrasonics ferroelecrics and frequency control, 1995.
[10] Pavlakovic, B. N., Leaky guided ultrasonic waves in NDT, Ph.D. dissertation, Imperial College London, 1998.
[11] Aristégui, C., Lowe, M. J. S. and Cawley, P., Guided waves in fluid-filled pipes surrounded by different fluids, Ultrasonics 39, 367–375, 2001.
[12] Long, R. S., Cawley, P. and Lowe, M. J. S., Acoustic wave propagation in buried iron water pipes, Proc. R. Soc. A 459, 2749–2770, 2003.
[13] Vogt, T., Lowe, M., & Cawley, P., Measurement of the material properties of viscous liquids using ultrasonic guided waves, IEEE Trans. Ultrason. Ferroelectrics Frequency Control, 737-747, 2004.
[14] Ma, J., Lowe, M.J.S. and Simonetti., F., Measurement of the properties of fluids inside pipes using guided longitudinal waves, Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on 54(3) 647-658, 2007.
[15] Elvira-Segura, L., Acoustic wave dispersion in a cylindrical elastic tube filled with a viscous liquid, Ultrasonics 37, 537-547, 2000.
[16] Baik, K., Jiang, J., & Leigthon, T. G., Acoustic attenuation, phase and group velocities in liquid-filled pipes: Theory, experiment, and examples of water and mercury, J. Acoust. Soc. Am., 128, 2610–2624. 2010.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article presents the impact of soil on the attenuation of the vibration signal.
1. It would be a great help for the reader if the author provides any information on the elastic modulus of soil normally found on sites/outdoors or if there are any specific limits/ranges of elastic modules of soil normally found outside. Does the rain have any impact on the elastic modulus of soil (Dry vs wet)?
2. Is Formula 12 applicable for all pipe materials including MDPE and other plastic pipes?
3. Does the size of the leak such as large or small have any impact on the attenuation of signals?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I'm not satisfied by the revised version, and I found a "signal processing" language not at the level of a scientific journal.
These are my comments to the few modifications
----> Your response to the existing literature
====> my comments
response not arrived.....
----> Your response 2, about the spectral analysis
"The purpose is to study which frequency band signal has a higher detection value. That is to say, we are studying which frequency band signal can travel farther"
====> My comments
How do you measure the "higher detection value"?
Why don't you show the full spectrum?
Figures 9 and 10 are misleading and againts your (and literature) conclusions of an exponential decay with distance and with frequency, and I suspect they are mainly related to noise. This analysis makes the whole paper not convincing and the results unreliable
----> Your response 3
"In some studies, the leakage signal of the numerical analysis part does not use the actual leakage signal but only the analog signal. The analog signal cannot cover all the actual signal's characteristics, and its method's effectiveness for replacing the pipeline leakage signal must be further considered"
"The calculation rules are as follows: since signals with different frequency components have reached 10m in the 0.07-0.11s time interval, which can reflect the amplitude of the whole signal, 1/3 of the average amplitude in this interval is used as the standard, and to remove certain randomness, the speed at which the signal amplitude reaches the amplitude standard for the second time is taken as the group velocity”.
====> My comments
What is the "analog signal"?
What does it mean "the standard"?
I completely do not understand how you can remove the randomness by selecting the second amplitude peak (??): why don't you perform a crosscorrelation? You claim in the paper you are adding the management of attenuation and dispersion: the best solution will be to compensate their effect and perform a crosscorrelaton.
----> your response 4, about the novelty
"Compared with previous studies, our innovations are mainly in the following aspects: a. We used the combined method of test and numerical simulation; b. We conducted a joint analysis of time-frequency signals; c. We proposed the relationship between the signal attenuation rate law, propagation distance, and soil around the pipe; d. We studied the influence of different soils on pipeline leakage signals' phase velocity and group velocity.
====> My comments
a. All good scientific papers combine and validate tests with numerical simulations
b. The joint analysis of time-frequency signals shows misleading figures, in contrast with the conclusions
c. there are no numerical/experimental validation of the propagation parameters vs soil properties. Moreover, the COMSOL simulations have been run with a perfect elastic medium, so neglecting the absorption, which is one of the objectives of the paper...
d. velocity computation is done in a "naive" way, and it is unreliable.
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I think the paper cannot be accepted for publication and its scientific level is far from the one of "Sustainability"
I suggest a complete revision and upgrade of the document in a new submission, with a correct positioning within the actual state of art, and more focused on the simulation of different scenarios, trying to obtain experimental "trends", such as pressure transient peak amplitude decay with distance and frequency for varying pipe rigidity, soil elastic parameters, etc.
