Effect of a Commercial Air Valve on the Rapid Filling of a Single Pipeline: a Numerical and Experimental Analysis
, Mohsen Besharat 2, Vicente S. Fuertes-Miquel 3 and Helena M. Ramos 2Round 1
Reviewer 1 Report
The paper exposes a numerical model to analyse the influence of an air valve in a pipeline during the filling operations. This model has also been validated by means of several experimental tests in laboratory. The topic of the paper is interesting, methodology (mathematical model and experimental equipment) and results are well described. The structure of the document is correct and the english style is proper. From this reviewer’s point of view, the following comments could improve the quality of paper:
-Details about the main characteristics of the mathematical model should be added in the abstract.
-Lines 35-36: please, complete with references.
-Line 38: in the sentence ‘In a study, Azoury et al [1] studied…’, remove ‘In a study,’.
-Line 41: 'CFD' should be defined previously
-Line 68: ‘The air valves are studied by…’ should be rewritten as ‘The air valves have been studied by…’
-Line 73: it would be very worth if the problems observed by the authors in their previous work (reference 30) were summarized here as well.
-Line 88: remove ‘(see Figure 1)’ is repeated in line 86.
-Line 163: ‘Lisbon, Portugal’ between brackets.
-Lines 174-175, sentence ‘which send…. on a computer.’ should be removed, this explanation is not interesting for the paper.
-Line 179: remove the coma after ‘HT pressure’.
-It would be very illustrative if Figure 3 is completed with a real photograph of the laboratory installation.
-In section 3.2, the total length of ‘sloped pipe branch’ should be included for comparing with the air pocket extension.
- Line 207: not perpendicular air-water interface to the main direction of the pipe installation should be also highlighted in Conclusion, since it is one of the main drawbacks of the model.
-Although the influence of the hydro-pneumatic tank pressure is the most relevant, the discussion of the results of Figure 4, especially the analysis of tpeak, can be completed with a analysis of the influence of x0. Moreover, the adjustments between numerical and experimental results are slightly better in the cases of x0=1.36.
-Lines 234-235: should be emphasized that the mathematical model reproduces properly the first oscillation and the maximum value but it is not valid for the rest of the response. This idea should also be included in conclusions.
-Figure 7 is complex to understand, probably it would be more easy to collect the results in a table.
-Conclusions should be completed with other relevant ideas that have appeared along the paper.
-The style of References should be uniform, i.e. year between brackets in all cases. Some relevant data have been omitted in the following references, they should be completed: 12, 14, 17, 20, 22…
Author Response
To: Reviewer #1
August 26, 2019
Dear Sir,
First of all, I would like to acknowledge you for the time you spent reading and reviewing the paper. I sincerely appreciate your comments.
I will try to explain the changes I made in the manuscript to adapt it to your suggestions.
Review suggestion: - Details about the main characteristics of the mathematical model should be added in the abstract.
Authors’ comments:
R.\ The following sentence was included in the new manuscript: “which is based on the mass oscillation equation, the air-water interface, the polytropic equation of the air phase, the air mass equation, and the air valve characterization.”
Review suggestion: - Lines 35-36: please, complete with references.
Authors’ comments:
R.\ The following reference was included:
Abreu, J.; Cabrera, E.; Izquierdo, J.; García-Serra, J. Flow Modeling in Pressurized Systems Revisited. J. Hydraul. Eng. 1999, 125, 1154–1169.
Review suggestion: -Line 38: in the sentence ‘In a study, Azoury et al [1] studied…’, remove ‘In a study,’.
Authors’ comments:
R.\ It was removed.
Review suggestion: -Line 41: 'CFD' should be defined previously
Authors’ comments:
R.\ It was defined.
Review suggestion: -Line 68: ‘The air valves are studied by…’ should be rewritten as ‘The air valves have been studied by…’
Authors’ comments:
R.\ It was rewritten.
Review suggestion: -Line 73: it would be very worth if the problems observed by the authors in their previous work (reference 30) were summarized here as well.
Authors’ comments:
R.\ The previous work only contains a brief explanation of hydraulic and thermodynamic formulations. The following sentence was included in the new manuscript: “This research explains in details the mathematical model including all hydraulic and thermodynamic formulations in comparison to a previous publication [31]. This research tackles the experimental and numerical study of the filling process……”.
Review suggestion: -Line 88: remove ‘(see Figure 1)’ is repeated in line 86.
Authors’ comments:
R.\ It was removed.
Review suggestion: -Line 163: ‘Lisbon, Portugal’ between brackets.
Authors’ comments:
R.\ Brackets were included.
Review suggestion: -Lines 174-175, sentence ‘which send…. on a computer.’ should be removed, this explanation is not interesting for the paper.
Authors’ comments:
R.\ The sentence was removed in the new manuscript.
Review suggestion: -Line 179: remove the coma after ‘HT pressure’.
Authors’ comments:
R.\ The coma was removed in the new manuscript.
Review suggestion: -It would be very illustrative if Figure 3 is completed with a real photograph of the laboratory installation.
Authors’ comments:
R.\ The photograph of the experimental facility was included in the new manuscript.
Review suggestion: -In section 3.2, the total length of ‘sloped pipe branch’ should be included for comparing with the air pocket extension.
Authors’ comments:
R.\ The information was included in the new manuscript: “….. were defined in the 1.50-m-long sloped branch pipe in…..”
Review suggestion: - Line 207: not perpendicular air-water interface to the main direction of the pipe installation should be also highlighted in Conclusion, since it is one of the main drawbacks of the model.
Authors’ comments:
R.\ Completely agree. The following sentence was included in the Conclusion Section: “however, the mathematical model is not valid for the rest of the transient response since the impact between the water column and the blocking water column produces a complex phenomenon, where the air-water interaction is not perpendicular to the main direction of the water pipeline.”
Review suggestion: -Although the influence of the hydro-pneumatic tank pressure is the most relevant, the discussion of the results of Figure 4, especially the analysis of tpeak, can be completed with a analysis of the influence of x0. Moreover, the adjustments between numerical and experimental results are slightly better in the cases of x0=1.36.
Authors’ comments:
R.\ Completely agree. The following sentences and Table 2 were included in the new manuscript:
”The greater the air pocket size (x0), the higher values of tpeak are reached.”
“A summary of experimental results is presented in Table 2, which shows a comparison between maximum values of air pocket pressure head, air pocket size, and attained tpeak. “
Table 2. Summary of experimental results
|
Test No. |
Maximum value of air pocket pressure head (m) |
(m) |
tpeak (s) |
|
1 |
15.0 |
0.96 |
0.55 |
|
2 |
15.0 |
1.36 |
0.58 |
|
3 |
21.4 |
0.96 |
0.50 |
|
4 |
21.4 |
1.36 |
0.52 |
|
5 |
29.3 |
0.96 |
0.46 |
|
6 |
29.1 |
1.36 |
0.49 |
|
7 |
46.9 |
0.96 |
0.40 |
|
8 |
44.9 |
1.36 |
0.44 |
Review suggestion: -Lines 234-235: should be emphasized that the mathematical model reproduces properly the first oscillation and the maximum value but it is not valid for the rest of the response. This idea should also be included in conclusions.
Authors’ comments:
R.\ The following sentence was included after lines 234-235: “It is important to note that the mathematical model reproduces properly the first oscillation and the maximum absolute pressure, but it is not valid for the rest of the hydraulic event.” . Also, in the Conclusion this idea was mentioned.
Review suggestion: -Figure 7 is complex to understand, probably it would be more easy to collect the results in a table.
Authors’ comments:
R.\ Table 3 was included in the new manuscript.
|
Test No. |
Air pocket pressure head (m) |
Peak reduction percentage (%) |
|
|
Without air vale |
Using the air valve S050 |
||
|
1 |
15.9 |
15.0 |
5 |
|
2 |
16.0 |
15.0 |
6 |
|
3 |
23.6 |
21.4 |
9 |
|
4 |
23.1 |
21.4 |
7 |
|
5 |
32.2 |
29.3 |
9 |
|
6 |
31.4 |
29.1 |
7 |
|
7 |
51.1 |
46.9 |
8 |
|
8 |
47.4 |
44.9 |
5 |
Review suggestion: -Conclusions should be completed with other relevant ideas that have appeared along the paper.
Authors’ comments:
R.\ More sentences were included in the conclusions:
…….however, the mathematical model is not valid for the rest of the transient response since the impact between the water column and the blocking water column produces a complex phenomenon, where the air-water interaction is not perpendicular to the main direction of the water pipeline
……
The relieve percentages of the maximum air pocket pressure are obtained because the air valve S050 presents a small outlet orifice of 3.175 mm.
The mathematical model can be used to compute the maximum air pocket pressure during filling processes using both undersized and well-sized air valves. However, the analysis of oversized air valves is not covered using the mentioned formulations since more extreme pressure surges can be achieved depending on air pocket size and initial hydro-pneumatic tank pressure.
Review suggestion: -The style of References should be uniform, i.e. year between brackets in all cases. Some relevant data have been omitted in the following references, they should be completed: 12, 14, 17, 20, 22…
Authors’ comments:
R.\ Te style of References was replaced according to guidelines of the journal.
I hope with the changes we did in the paper and the explanations above the paper will look better. Thanks one more time for your time and patience reviewing our paper.
Yours sincerely,
Oscar E. Coronado-Hernández
Ph.D
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The reviewer wants to thank the authors for their paper about the comparison of numerical modelling and experimental investigation of the fast filling of a pipe (compressed air pocket) He/she has some questions to ask:
Line (L) 40: and instead of & and there is a dot missing after Saemi et al L69: It is not clear how the initial mathematic model, which was published in [30], is different from the later presented one in Section 2. The reviewer couldn’t access the literature [30], but nevertheless, it should be clearly shown, what the novelty of the paper is and that it is not only a reproduction of the conference paper. The section 2 includes no literature references. This would imply that the complete theoretical concept is new. The reviewer would suggest to add key sources of the concept. L163: Again. The experiments are first published in this paper? If not, please add the references. Figure 3 the other end of the pipe (x bigger 3 m) is closed? L176: 0.5% of what? The reviewer assumes that it is the maximum pressure. How big is the error of the mathematic model in relation to this? Please also provide the used measurement frequency as well as the exact location of the pressure transducer in [m] over datum. Figure 4: please change the scaling on the y-axis so that the difference can be seen and also quantify this (for example max value or other statistic values) References need some work and please check the journal guidelines.
The reviewer would like to motivate the authors to clearly present the novelty of the paper and is looking forward to read the paper again in detail.
Author Response
To: Reviewer #2
August 26, 2019
Dear Sir,
First of all, I would like to acknowledge you for the time you spent reading and reviewing the paper. I sincerely appreciate your comments.
I will try to explain the changes I made in the manuscript to adapt it to your suggestions.
Review suggestion: Line (L) 40: and instead of & and there is a dot missing after Saemi et al
Authors’ comments:
R.\ The dot was included in the new manuscript.
Review suggestion: L69: It is not clear how the initial mathematic model, which was published in [30], is different from the later presented one in Section 2.
Authors’ comments:
R.\ The following sentence was included in the new manuscript: “This research explains in details the mathematical model including all hydraulic and thermodynamic formulations in comparison to a previous publication [31]”.
Review suggestion: The reviewer couldn’t access the literature [30], but nevertheless, it should be clearly shown, what the novelty of the paper is and that it is not only a reproduction of the conference paper.
Authors’ comments:
R.\ The conference paper only shows the mathematical model, but it does not contain neither any experimental result nor its validation.
Review suggestion: The section 2 includes no literature references. This would imply that the complete theoretical concept is new. The reviewer would suggest to add key sources of the concept.
Authors’ comments:
R.\ Some references were included in this section.
Review suggestion: L163: Again. The experiments are first published in this paper? If not, please add the references.
Authors’ comments:
R.\ Only four experiments were published in a Spanish Conference Paper entitled “modelo numérico del proceso de llenado de una conducción simple con válvula de aire” in the XVI Seminario Iberoamericano de Redes de Agua y Drenaje, SEREA 2019. This conference paper only contains a brief explanation of the mathematical model as well as a short analysis of results and experiments. This conference has a no important international contribution on research.
On the other hand, the current manuscript contains a deep explanation of the mathematical model as well as includes the complete experiments to validate the mathematical model.
Review suggestion: Figure 3 the other end of the pipe (x bigger 3 m) is closed?
Authors’ comments:
R.\ In Figure 3 was included a valve in X=3.0 m. This valve is closed during all experiments.
Review suggestion: L176: 0.5% of what? The reviewer assumes that it is the maximum pressure. How big is the error of the mathematic model in relation to this? Please also provide the used measurement frequency as well as the exact location of the pressure transducer in [m] over datum.
Authors’ comments:
R.\ The error corresponds to the maximum pressure. It was included in the new manuscript. The error of the pressure transducer is so slow compared to the attained maximum pressure. The following comment was included: “This measurement error is negligible compared to the maximum pressure values attained”
The following information was included in the new manuscript: “located at Y=0.8 m and X=0.0 m, which has frequency of data collection of 0.0062 s”.
Review suggestion: Figure 4: please change the scaling on the y-axis so that the difference can be seen and also quantify this (for example max value or other statistic values)
Authors’ comments:
R.\ All subfigures have the same scale; however, for subfigures a) and b) a zoom in was included in order to identify maximum values.
Review suggestion: References need some work and please check the journal guidelines.
Authors’ comments:
R.\ The style of references was improved according to journal guidelines.
I hope with the changes we did in the paper and the explanations above the paper will look better. Thanks one more time for your time and patience reviewing our paper.
Yours sincerely,
Oscar E. Coronado-Hernández
Ph.D
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Thank you for the answers and the corrections. The paper is fine. Looking forward to the publication.
