Experimental Study on Surface Erosion of Grade A Marine Steel by Ultrahigh-Pressure Water Jet
Round 1
Reviewer 1 Report
Journal: Water
Publisher: MDPI
Manuscript Title: Experimental study on surface erosion of Grade-A marine steel 2 by ultra-high pressure water jet
Manuscript ID: water-1740682
I have gone through the manuscript. It is quite interesting, but few clarifications and improvements are to be incorporated to enhance the quality of the paper.
1. Refer Line Number: 19-20
Please change the statement: “The simulation results are in good agreement with the 19 simulation results.”
2. The manuscript will be more interesting if the authors include a figure to describe the high speed water jets depicting the regions close to the nozzle, water mist zone, and diffused droplet region etc.
3. Characteristics of ultra-high pressure water jet is repeated twice in the abstract: 200 MPa, 40L/min
4. http://hdl.handle.net/10210/425958, this paper proved that the jet pressure is the factor that has the greatest impact on the surface quality, and the material surface quality is the best when the pressure is 350 MPa.
Why did you choose the characteristics of water jet as: 200 MPa, 40L/min?
Please mention if there is some literature/industrial basis.
5. Could you able to forecast the influence of nozzle diameter on the surface erosion due to high-pressure water jet technology?
6. How did you investigate the changes in properties of surface layers due to high-pressure water jet technology?
7. Explain the influence of the angle of impingement, water jet velocity, standoff distance, and erodent discharge on the surface erosion rate high-pressure water jet technology.
8. Elaborate the physics behind the microhardness, propagation of microcracks and fractures in the material caused by high-pressure water jet.
9. Please cite this article: https://0-doi-org.brum.beds.ac.uk/10.3390/coatings12040482 as it investigates the water jet erosion performance.
10. In Figure 11 authors depicted the SEM images of sample surface impacted by jet at 200MPa pressure when the impact time is 40 s and 50 s respectively.
Could you trace the cavitation erosion pit and intergranular crack when the impact time is 50 seconds?
11. The manuscript did not explain the governing equations and solution methodology: this is very important as a multiphase model has to be chosen to account air-water phases involved due to the high-speed water jets.
What modification should be done in the governing equations to simulate the air entrainment process in the high-speed water jets?
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Comments for author File: 
Comments.pdf
Author Response
We are very grateful to Reviewers for reviewing the paper so carefully. We have carefully considered the suggestion of Reviewers and make some changes.
Author Response File: Author Response.pdf
Reviewer 2 Report
Dear Authors
To improve the quality please see my indications below. I have found some inaccuracies and deficiencies. In some places in CFD section the information is lacking or very poor and the explanation and not clear for a reader. It requires an improvement. Please, see also your originally submitted file (if you have not received it, please contact Editor). When you answer all questions and correct shortcomings, please write explanations in the paper as much and as clear as possible.
Below I present only general remarks as the most important and critical points concerning the quality of paper.
General remark. In my opinion the paper is more suitable to MDPI ‘Materials’. I have an impression that the Author(s) that wrote paper know(s) more about materials than about CFD (I even feel this paper could be written without CFD results and it would be sufficient). I leave it to an Editor decision.
Introduction suffers from missing papers concerning peening of materials or papers concerning the relation between numerical and experimental investigations. I suggest to introduce some papers to Introduction regarding this (e.g. see papers of Soyama). Please consider it.
Chapter 2.2. This chapter is very poor in information. Nothing is written down about Y+ applied. Lower picture in Fig.2 looks like it is cut? Isn’t it? If yes, why isn’t the entire domain presented? These all should be explained/revised in the text.
Chapter 2.3. What was turbulence model used in calculations?
General remark. The validation of the mesh influences should be presented. The pressure difference used (200 MPa) is of a huge value, which is not trivial for the results. Please justify how do you trust your mesh?
Names of chapters 4, 4.1, 4.1.1. The names contain first small or big letters. Generally, there is a disorder. Should be corrected.
L121. ‘was 60°’. Fig.5 suggests that 90° was also used.
Chapter 3.1. The positions of strain gauges are not shown. Fig.4b does not explain it. Please revise this text carefully. This is quite important for the measurement quality. Please explain what Fig.4a presents. This is not clear.
Fig.5. Pictures in figure should be enlarged. Additionally, the area of nozzle should be zoomed in as it is heart of experiment. Now the results quantitatively are not readable. The same concerns all figures with CFD results presented further.
L183. “Numerical simulations were carried out for models with different target distances with constant internal parameters of the nozzle.” It is not clear and requires explanation in the text. What models? What target distances? What ‘constant internal parameters of the nozzle’? Please describe it all precisely in the text.
General remark. As MDPI does not limit the number of pages, I suggest to enlarge all figures (as mentioned especially with numerical results).
Fig.6. Define target distances in Figure 2 or in another way. It should be added to text.
L199. What does ‘certain angle’ mean? It is highly not precise description. What angle was used in calculations? The information is very sketchy about carried out calculations. Please extend the text regarding this.
L199. “Therefore, choosing the appropriate angle of incidence can reduce the energy loss of the jet to a certain extent.” This is not proven sentence in the text. Were the calculations carried out regarding this? Was the optimal angle found?
Fig.8. The jet should be zoomed in to show the details of flow around it.
L206. “…the dynamic strains at the three test points…”. What are the three test points? This requires to be explained.
L207. “… and the output graphs overlap.” What does it concern to? Please explain it.
L256. “… sample 2 began to be damaged under impact for 40 s. In sample 3, the jet loading region was completely destroyed…” The terms 'began to be damaged' and 'was completely destroyed' require deeper explanation how to understand it. E.g. what does ‘completely destroyed' mean? Is there a meaning concerning the area or depth of eroded material? Please explain it carefully in the text.
L279-281. “Combined with the simulation data, it can be concluded that the dynamic pressure attenuation from the center to the edge of the 200 MPa ultra-high pressure water jet is small, and the pressure difference can be ignored.” This is very important sentence but in my opinion is not sufficiently proven. Please discuss in the text what it means exactly. Especially explain, why ‘the pressure difference can be ignored’?
Conclusions. L348. “…at a certain Angle…” What angle? The same with “…can be reduced to a certain extent…”. It is not understood and makes it very mysterious. Please explain what it means. In the scientific paper everything should be clear for a reader.
Conclusions. L356. This statement, as stated above, requires explanation in the text. It could be good to present/prove it in the picture why ‘the pressure difference can be ignored’. Generally, the figures of CFD are of a poor quality (nothing is seen exactly). Please modify them accordingly.
Comments for author File: Comments.pdf
Author Response
We are very grateful to Reviewers for reviewing the paper so carefully. We have carefully considered the suggestion of Reviewers and make some changes.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper reports both experimental and numerical results related to surface erosion of Grade-A marine steel by a ultra-high pressure water jet. My opinion is that it requires major revision before it can be suitable for publication.
First of all, the use of English is very poor and many sentences just can not be understood. I suspect that the paper has been translated to English using an automatic translation software of the kind which is presently available (Google translate, Deep L translate, ....). A typical example is provided by line 161 ("Figure 5(b) for the jet velocity cloud, it can be seen in a certain jet distance within the core velocity ...."). Therefore, the use of English must be thoroughly verified and corrected everywhere this is needed !
Then, the numerical method which is implemented must be described and discussed in a much more detailed and precise way. For instance, line 151 claims that "The occurence of cavitation in the nozzle is closely related to its geometric structure, according to Bernoulli's equation, the flow velocity of a cross-section ....". This is just a very general comment but absolutely nothing is said about the equations, the way cavitation is accounted for, how bubbles (or vacuoles as indicated for instance in line 155) are considered and tracked within the flow, and so on. Later on (line 156), comments address turbulence and cavitation modeling, but absolutely nothing is said about the choice and the validation of such modeling. The same is true about he meshing which is probably a very important issue for such a situation of an ultra-high pressure water jet impacting a plate.
Finally, concerning the experimental results, quite a few comments are made about cracks, peeling pits, and so on, but these events are not described in a precise way : how are they defined, how are they identified on the images, what is the likely inaccuracy, and so on ?
Author Response
We are very grateful to Reviewers for reviewing the paper so carefully. We have carefully considered the suggestion of Reviewers and make some changes.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Authors have addressed my queries and required changes are made in the manuscript.
hence, the manuscript may be accepted for publication.
Author Response
Dear Reviewer:
We are very grateful to you for reviewing the paper again. Once again, we thank you for your revision and help to our paper. We sincerely hope that this article can be successfully published in water journal.
Cheng Shu-ming
2022.06.14
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear Authors
1) I expected some more references.
2) I still suggest to present the areas of jet (Fig.6, 7, 9) on separate picures (only jet shown zoomed in). The area of blue color brings nothing interesting into paper.
With best regards
Author Response
Dear Reviewer:
We are very grateful to you for reviewing the paper again. We have carefully considered the suggestion of you and present the areas of jet (Fig.6, 7, 9) on separate picures.Once again, we thank you for your revision and help to our paper. We sincerely hope that this article can be successfully published in water journal.
Cheng Shu-ming
2022.06.14
Author Response File: Author Response.docx
Reviewer 3 Report
I have now read the revised version of the paper, together with the authors' replies to my comments. I am satisfied with all. However, a few details must still be corrected :
- at the bottom of page 4 (section 2.2.3) : what is Qsas ? What is it used for ?
- at the top of page 5, the sentence "Grid diagram was to facilitate the display of the nozzle near the wall of the grid" must be corrected because it is not possible to understand its meaning in its present form. What is "the wall of the grid" ?
- at the bottom of page 7, I think there is (at least) one error in the figure numbers. I suspect that figure 5(a) should be figure 6(a). However, all the numbers should be checked.
Author Response
Dear Reviewer:
We are very grateful to you for reviewing the paper again.
First ,the SAS term in ω equation is defined as QSAS , it is the turbulence transport equations of turbulent frequency. Second,the sentence "Grid diagram was to facilitate the display of the nozzle near the wall of the grid" have been revised to “Image of the mesh shows the boundary layer grids in the nozzle”.Last, we have changed “5(a)” to “6(a)”and all the numbers have been checked in this paper.
Once again, we thank you for your revision and help to our paper. We sincerely hope that this article can be successfully published in water journal.
Cheng Shu-ming
2022.06.14
Author Response File: Author Response.docx
