Study on the Transient Flow Characteristics of a Hump Water Pipeline Based on the Random Distribution of Bubbles
, Jianyong Hu 1,3,*, Mingming Song 1,3, Hui Shen 1,4, Yu Zhou 5, Dongfeng Li 5 and Feng Xie 5Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsFirst of all the authors need to rewrite this paper, or give it to translate to a native speaker. Now the paper is hard to understand. The introduction needs to be extended and the aim of the work better formulated. The stages of proposed research design need to be clearly explained. Similarly, authors need to explain better the methods they used and clearly present their results. My detailed comments are:
1) Line 14-19: This sentence is so long that it is hard to read and understand it. Please do not use such complicated sentences in this work.
2) line 39-42: The same as in Abstract this sentence is to long You are using twice and - it's hard to read
3) line 172 - what means FS?
4) line 151: Its not a drawing its a picture
5) line 156: exhoust pressure is 8kg? kg are the units of mass?
6) line 163: its not a diagram its a picture!
7) line 172 - what means FS?
8) line 177 - once again diagram - correct to picture
9) line 190: "belive" - such a word should be unuse in technical science. You need to prove someting, we can not belive. Give a reference that someone before You wrote that Engineers belive.
10) line 196: What means Outlet pressure in table 2 that value is 0 (is it perfect vacuum?). Pressure should be displayed as absolute pressure value.
11) line 202: "Finally" - You just started it a long road to a final?
12) linie 211: what means mi and sigma square on this figure explain in the manuscript
13) line 224: its not a 3-D domain model - You need to rewrite this Figure description
14) line 258: eq. 5 what sum is it? on which section is calculated , is q a changable number of elements - its totally unclear
15) line 254 and 255 - so there is no difference between alfa and rho as the authors writes that both are the volume fraction; instead where they evidently have liquid and gas phase dynamic viscositoes they mentione abut density.
16) line 251: mixing velocity (not speed)
17) line 246: rho is rather the fluid density. What thq means
18) line 243: "does not involve" or should be "does involve"?
19) line 292: so You mean Fluent?
20) line 280: Intensity - it should be density.
21) line 270: what reference helped to select 1.42; 1.68 and 0.09 constats values. What values takes S_k and S_epsilon such to fit simulation results to experimental?
22) line 321: what kind of quantitative model was used. I only read about "results are within the error range" The fit was not great if a properly done qualitative comparison was done it would be shown. Fit between numerial and experimental was in my opinion poor. Of course maybe the mean vales of pressures are on the same level in the selected time range by the authors...
23) line 311: the length of manuscripts in MDPI journals is not restricted, so You are welcom to compare at least one -two more cases in revised version of this paper.
24) The figures 14-16 are so small that its hard to see anything, please enlarge them.
25) line 402: do You compare experimental results or only numerical. You should compae both of them!
26) line 433: I do not understand the authors selection of cases to comparison. Here we see they analyze pressures for cases 1-4 while earlier they analazed many other cases up to Case 12.
27) Figures 14 to 16 are so small that I do not see anything. Thats why its hard for me to check the authors description of the phenomenas simulated.
28) line 509: Try in revised version to cite more recent works. Some papers about cavitation that can enrich the introductions are:
a) High-Speed Imaging of Water Hammer Cavitation in Oil–Hydraulic Pipe Flow
https://doi.org/10.3390/fluids7030102
b) Modeling Transient Pipe Flow in Plastic Pipes with Modified Discrete Bubble Cavitation Model
https://doi.org/10.3390/en14206756
c) CFD Investigations of Transient Cavitation Flows in Pipeline Based on Weakly-Compressible Model
https://doi.org/10.3390/w12020448
d) Concerning Dynamic Effects in Pipe Systems with Two-Phase Flows: Pressure Surges, Cavitation, and Ventilation
https://doi.org/10.3390/w14152376
e) Cavitation Erosion Characteristics for Different Metal Surface and Influencing Factors in Water Flowing System
https://doi.org/10.3390/app12125840
etc.
29) line 506: such a acknowledgment can be written after the review process - before it You (authors) do not know if the review process will be constructive or not :)
The paper need major specialized linguistic improvements - now it was very hard to read it.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors presented a numerical and experimental study on the Transient Flow Characteristics of Hump Water Pipeline Based on the Random Distribution of Bubbles.
The paper is interesting and can be accepted for publication after addressing the following points:
The main quantitative results are to be mentioned in the abstract.
The novelty of the paper is to be clearly stated.
A reference is to be added to Fig 1.
For the experimental study:
- more details on the measurement techniques and data acquisition system are to be provided.
- An experimental uncertainty study is to be performed.
- For the visualization of the flow it will be interesting to use an optical laser system.
For the numerical study:
The boundary conditions are to be expressed mathematically.
Have you solved 2D or 3D configuration?
The used turbulence model is to be justified.
What is the considered range for Reynold number?
A qualitative (2D profiles for example) verification of the numerical model is to be performed by comparing with previously published numerical results.
What is the convergence criterion?
What is the time step?
Information about the characteristics of the used computer and computational time are to be provided.
In Fig 2, the numerical and experimental results are not similar; how can you explain that?
In Fig 13 why is the time limited to 1.5 seconds.
The scientific soundness is to be improved by adding more physical interpretation to the discussion
English level should be improved
Comments on the Quality of English Language
English level should be improved
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis paper discusses the study of the transient flow characteristics of hump water pipeline in presence of air bubbles in the water flow and in absence of air expulsion from the pipe.
Physical tests concern the statistical characterization of the distribution of air bubbles in terms of size and number; pressure patterns at different fractions of the air volume within the liquid phase are also identified.
Together with physical tests, the results of CFD numerical simulations are presented, using a CLSVOF two-phase flow model coupled with a RNG k-e turbulence model, to analyse the temporal evolution of flow and pressure patterns in the two-phase flow.
The related work is an interesting topic, and also with great complexity and challenge.
The numerical results are good, although there are some differences with the experimental pressure oscillations. The research work and contributions are worthful.
I suggest that the article is accepted with some improvements and revisions.
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Figure 13 shows the comparison between the experimental and numerical pressure patterns in relation to Case 12 alone. In my opinion, it is also important to show the comparison between experimental and numerical results for all other cases with the presence of air (Cases 2, 3, 4, 6, 7, 8, 10 and 11, as was done for the numerical results alone in subsequent figures, such as in Figures 14-15-16).
The comparison of all cases is necessary to check whether the differences in pressure fluctuations between experimental and numerical data are also present in the other patterns.
For the same reason, the evaluation of the dimensionless number DH' given in equation (13) must be done not only for the results of the numerical analyses, as carried out in the paper, but also for the experimental data, in order to highlight the correspondence of results in terms of pressure oscillation characteristics.
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L100: the number of the article cited in the bibliography is wrong.
L106: the number of the article cited in the bibliography is wrong.
In Table 1, the unit of measurement of pump power is incorrectly written: (kW) instead of (KW).
In Table 2, the unit of measurement of outlet pressure is written incorrectly: replace (Pa) instead of (pa).
L155, L171: error in the pressure measurement unit: replace MPa instead of Mpa (Pascal=Pa with a capital letter).
L174: Delete space in “3m s”.
Figure 6 shows 3 different bubbles distributions within the horizontal section of the “hump”, but in the 3 pictures the axis of the pipe is arranged vertically. For a clear identification of the phenomenon, it is advisable to arrange the 3 images with the axis of the pipe horizontally.
#3 .2.1: There are some parameters reported in the equations that are not defined: of equation (1);
,
,
and
of the equations (7), (8) and (11);
of the equations (7) and (8); );
and
of the equations (10) and (11).
L246÷L248, L251÷L252, L254÷L256: there are some punctuation mistakes: there is no space after the “:” and the “;”.
L270: the parameters ,
and
are presented but in equation (8) there are the parameters
,
and
.
In Table 3, the density is shown with the name “Intensity”.
For equation (12), the parameters and
are not defined
L313: Case 12 has a fraction of the air volume equal to 0.15 and not 0.85.
In Figures 17, 18 and 19 the unit of measurement of pressure is written incorrectly: replace (Pa) instead of (pa).
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
1) this description under eq. (4) and (5) is still wrong:
"Where :?? and, ??, - denotes the liquid- phase volume fraction and the gas- phase volume fraction, respectively; ?? and, ??,- denotes the liquid- phase volume fraction and the 303
gas- phase volume fraction, respectively; and ?? and, ??, - denote thes liquid-phase density and gas-phase viscosity density, respectively. "
2) The reference to eq. (6) and (7) is missing;
3) Figure 13 and others - what is analyzed Pressure than please add "p (Pa)" symbol on y axis so the reader knows what is analyzed.
4) Still more analysis about experimental research is needed - even in this paper - not wait untill the next one.
5) I and future reader still does not understand how the coefficients: "?1? , ?2? , and ?3? -are
empirical constants taken as 1.42, 1.68, and 0.09" are selected on what basis?
6) The reader espect some discution why the use of: "and ?? , and ?? are -user-
defined source terms." is needed;
7) The proposed in earlier references 5 (recent) was the minimum that the author should analyze and discuss, but I highly sugest they add around 10 new references in the introduction related to this topic.
even of the cost of deletion of the older ones. selection of just two is not an large improvement of introduction that I expected.
I noticed that some correction have been done. Anyway suggest the Journal translator to check this paper carefully as still many minnors errors is attached.
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors addressed the issues I raised.
The paper can be published in the present form.
Author Response
Thank you for your suggestions.
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors corrected some errors but should consider to correct other mentioned in my earlier review. I still noticed that this points needs corrections:
a) The vertical axis description on Fig. 13 and Fig. 17-19 are still wrong - now it is just the unit in paranthesis "(Pa)" and should be "p (Pa)".
b) Cite the literature in which the eq. (6) and (7) are derived or described in detail - have the authors derived this equation by themself? I do not think so.
c) "the default value in Fluent calculation software is adopted." and "The source term represents an unstable term that cannot be included in the control equation. In general, the source term is not constant, and the default source term of Fluent software is adopted in this paper." - write about it in the paper, not only in the rebuttal to the reviewer.
d) find two more new references from this field published just in 2023 and cite in the Introduction.
Author Response
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