Flow Field and Gas Field Distribution of Non-Submerged Cavitation Water Jet Based on Dual-Nozzle with Concentric Configuration

Round 1

Reviewer 1 Report

The manuscript investigated the flow field characteristics of cavitation water jets using numerical simulation. The influences of the nozzle dimension and the internal and external pressure on the flow field characteristics were discussed. I consider the content of this manuscript will meet the reading interests of the readers of the journal. However, there are figure illustration issues, and the discussion and explanation should be further improved. Therefore, I suggest giving a minor revision and the authors need to clarify some issues or supply more validation data to enrich the content.

1. Please develop a better title. This one does not state what is important to catch the prospective reader's attention.

2. The language requires major revision. The paper does not read smoothly (many typos) and it is redundant. Many grammar and Chinglish issues exist across the whole manuscript, e.g., line 479, "… is may not…". I suggest the authors consult a native English speaker.

3. The literature review part needs to be modified, and the current version of the literature is outdated. The authors should pay attention to the latest progress in this field, and some novel literature and methods are worth understanding and supplementing. The number of references is small, and the author should add several frontier articles.

4. In the Introduction, Since cavitation plays detrimental effects commonly, I suggest also introducing the relevant experimental works of cavitation. Kindly add the reference in the Introduction, of

-Sustainability 14.15 (2022): 9074. https://doi.org/10.3390/su14159074

- Applied Sciences 13.1 (2023): 613. https://doi.org/10.3390/app13010613

- Int. J. Heat Mass Transfer 170 (2021): 120970, https://doi.org/10.1016/j.ijheatmasstransfer.2021.120970;

- Journal of Cleaner Production (2022): 130470,

https://doi.org/10.1016/j.jclepro.2022.130470.8.

- Energy 254 (2022): 124426, https://doi.org/10.1016/j.energy.2022.124426;

- Ultrasonics Sonochemistry 86 (2022): 106035, https://doi.org/10.1016/j.ultsonch.2022.106035;

5. The quality of Fig 2 needs to be improved. Nothing can be seen clearly in Figs 2b,

6. The colour map shall be provided and be consistent in Figs 4 and 5.

7. Line 464, "…we can conclude that …has the better cavitation effect and impact pressure." What is the definition of "better cavitation effect"?

8. Conclusion does not reflect the novelty of this work. Please make sure your conclusions' section underscores the scientific value-added of your paper, and/or the applicability of your results. Highlight the novelty of your study. Clearly discuss what the previous studies that you are referring to are. What are the Research Gaps/Contributions?

Author Response

Dear reviewer 1,

Thanks very much for very good constructive criticism and comments on our paper. We have modified the manuscript accordingly, and the detailed comments are responded as follows:

Comments from reviewer 1:

1. Please develop a better title. This one does not state what is important to catch the prospective reader's attention.

Thanks for your carefully review and good suggestions. We have revised the title.

2. The language requires major revision. The paper does not read smoothly (many typos) and it is redundant. Many grammar and Chinglish issues exist across the whole manuscript, e.g., line 479, "… is may not…". I suggest the authors consult a native English speaker.

Thanks for your carefully review. We have checked the English grammars in detail. The language mistakes have been revised throughout the paper. And the English-related issues have checked by professional language editing service.

3. The literature review part needs to be modified, and the current version of the literature is outdated. The authors should pay attention to the latest progress in this field, and some novel literature and methods are worth understanding and supplementing. The number of references is small, and the author should add several frontier articles.

Thanks for your comments. We checked the relevant literature again and added some recent developments in the previous Introduction section.

4. In the Introduction, Since cavitation plays detrimental effects commonly, I suggest also introducing the relevant experimental works of cavitation. Kindly add the reference in the Introduction, of

-Sustainability 14.15 (2022): 9074. https://doi.org/10.3390/su14159074

- Applied Sciences 13.1 (2023): 613. https://doi.org/10.3390/app13010613

- Int. J. Heat Mass Transfer 170 (2021): 120970, https://doi.org/10.1016/j.ijheatmasstransfer.2021.120970;

- Journal of Cleaner Production (2022): 130470,

https://doi.org/10.1016/j.jclepro.2022.130470.8.

- Energy 254 (2022): 124426, https://doi.org/10.1016/j.energy.2022.124426;

- Ultrasonics Sonochemistry 86 (2022): 106035, https://doi.org/10.1016/j.ultsonch.2022.106035;

Thanks for your good comment. We have carefully read the references you suggested and added them to the Introduction section.

5. The quality of Fig 2 needs to be improved. Nothing can be seen clearly in Figs 2b,

Thanks for your time and efforts on our paper. We have updated Figure 2b and added a partial enlargement.

6. The colour map shall be provided and be consistent in Figs 4 and 5.

Thanks for your good comment. We will provide a clear original picture.

7. Line 464, "…we can conclude that …has the better cavitation effect and impact pressure." What is the definition of "better cavitation effect"?

Thanks for your good comment. In this paper, the cavitation effect is measured by the size of the cavitation cloud area in the flow field.

8. Conclusion does not reflect the novelty of this work. Please make sure your conclusions' section underscores the scientific value-added of your paper, and/or the applicability of your results. Highlight the novelty of your study. Clearly discuss what the previous studies that you are referring to are. What are the Research Gaps/Contributions?

Thanks for your good comment. We have revised the Conclusions section.

Author Response File: Author Response.docx

Reviewer 2 Report

1. What type of grid is utilized?

2. Please provide a concise explanation of what the Courant number is.

3. Please add the solution set up for simulation. For example, what is under relaxation factor for pressure, momentum, etc?

4. What does displaying the velocity distribution mean? Please provide more information. The author is expected to not only present the numerical results without connecting them to the system's actual performance.

5. Discretization in Fluent employs the finite volume method rather than finite element analysis. Please revise

6. Line 177-178. “Although some cavitation factors are ignored, it is easier to converge and saves computational resources.” Please specify which cavitation factors are neglected.

Author Response

Dear reviewer 2,

Thanks very much for very good constructive criticism and comments on our paper. We have modified the manuscript accordingly, and the detailed comments are responded as follows:

Comments from reviewer 2:

1. What type of grid is utilized?

Thanks for your carefully review. We use a two-dimensional structured grid. All meshes within the flow field are quadrilaterals.

2. Please provide a concise explanation of what the Courant number is.

The physical meaning of the Courant number is the ratio of the fluid motion distance to the unit length of the rectangular grid within the time step.

3. Please add the solution set up for simulation. For example, what is under relaxation factor for pressure, momentum, etc?

Thanks for your comments. The relaxation factors for pressure and momentum are both 0.75, and the rest of the relaxation factor parameters are shown in the figure below. We have modified it in the text (at line 142).

4. What does displaying the velocity distribution mean? Please provide more information. The author is expected to not only present the numerical results without connecting them to the system's actual performance.

Thanks for your good comment. We believe that the impact pressure in the cavitation jet includes the impact force of water jet and the impact force of cavitation bubble collapse. The velocity distribution in the flow field can help determine the action range of the water jet. Judging from the velocity distribution combined with the gas phase cloud image, the nozzles with expansion and contraction sections can not only increase the volume of cavitation cloud in the flow field, but also enhance the action distance of the water jet. Therefore, we believe that displaying the velocity distribution can help gauge the overall performance of a nozzle.

5. Discretization in Fluent employs the finite volume method rather than finite element analysis. Please revise

Thanks for your good comment. We have revised in the article.

6. Line 177-178. “Although some cavitation factors are ignored, it is easier to converge and saves computational resources.” Please specify which cavitation factors are neglected.

Thanks for your good comment. We have revised in the article.

Author Response File: Author Response.docx

Reviewer 3 Report

This research is valuable but needs some revision.

Comment No. 1: This paper should be edited grammatically.

Comment No. 2: You should add appropriate references for governing equations.

Comment No. 3: Does your geometry have a specific application in the industry?  (With same dimension)

Comment No. 4: The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

Comment No. 5: An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

Comment No. 6: You should add quantitative results to the abstract section.

Comment No. 7: How do you prove the time independence of your solution?

Comment No. 8: You should add your computer configuration and CPU time.

This research is valuable but needs some revision.

Comment No. 1: This paper should be edited grammatically.

Comment No. 2: You should add appropriate references for governing equations.

Comment No. 3: Does your geometry have a specific application in the industry?  (With same dimension)

Comment No. 4: The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

Comment No. 5: An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

Comment No. 6: You should add quantitative results to the abstract section.

Comment No. 7: How do you prove the time independence of your solution?

Comment No. 8: You should add your computer configuration and CPU time.

Author Response

Dear reviewer 3,

Thanks very much for very good constructive criticism and comments on our paper. We have modified the manuscript accordingly, and the detailed comments are responded as follows:

Comments from reviewer 3:

1. This paper should be edited grammatically.

Thanks for your carefully review. We have checked the English grammars in detail.

2. You should add appropriate references for governing equations.

Thanks for your carefully review. We have added references to the governing equations.

3. Does your geometry have a specific application in the industry? (With same dimension)

Thanks for your comments. Our coaxial dual-nozzle structure is currently experimental.

4. The originality of the paper needs to be stated clearly. It is of importance to have sufficient results to justify the novelty of a high-quality journal paper. The Introduction should make a compelling case for why the study is useful along with a clear statement of its novelty or originality by providing relevant information and providing answers to basic questions such as: What is already known in the open literature? What is missing (i.e., research gaps)? What needs to be done, why and how? Clear statements of the novelty of the work should also appear briefly in the Abstract and Conclusions sections.

Thanks for your good comment. We have revised the Introduction and Conclusions sections.

5. An updated and complete literature review should be conducted and should appear as part of the Introduction, while bearing in mind the work's relevance to this Journal and taking into account the scope and readership of the journal. The results and findings should be compared to and discussed in the context of earlier work in the literature.

Thanks for your time and efforts on our paper. We have revised the Introduction.

6. You should add quantitative results to the abstract section.

Thanks for your good comment. But it is a pity that we have not obtained specific numerical results for the time being in this paper. Therefore, we only include the main conclusions in the Abstract.

7. How do you prove the time independence of your solution?

Thanks for your good comment. For the time step, we first conduct a literature survey. According to the results of literature research, the time step is generally selected as 10E-5~10E-6. In addition, we verified the independence of time steps, and the results are shown in the figure below. Considering the calculation accuracy and calculation cost comprehensively, we believe that it is appropriate to select the time step as 10E-6.

(a) Time step:10E-4                           (b) Time step:10E-5

(c) Time step:10E-6                        (d) Time step:10E-7

Figure 1. Time Independence Verification.

8. You should add your computer configuration and CPU time.

Thanks for your good comment. The CPU used for the calculation is Intel(R) Xeon(R) Gold 6242R.The simulation calculation in this paper used a total of 2000 core hours.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Now it can be published.