Simulation Study on Thermal Wake Characteristics of Underwater Vehicle under Rotary Motion

Round 1

Reviewer 1 Report

Please see the attached file.

Comments for author File: Comments.pdf

Author Response

Dear reviewers and editors,

First of all, thank you very much for taking time out of your busy schedule to read and revise my article. I have carefully studied the reviewer's valuable comments and made the following modifications one by one according to the suggestions:

1. Domestic and foreign scholars have conducted in-depth theoretical and experimental studies on the thermal wake characteristics of underwater vehicles under direct navigation conditions, but most of them have not considered the impact of rotary motion on wake. In this paper, the underwater vehicle experiment platform was built to verify the numerical simulation method, and a rotary example was used to quantitatively process the floating process of thermal wake from two aspects: the movement trajectory of near-field cooling water and the spatial evolution of far-field thermal wake, so as to analyze the causes of the surface arc hot spots in detail. The thermal wake on the rotating side and the thermal wake on the deviating side are greatly affected by the whirlpool caused by the body, have different rotation directions, and experience different floating and diffusion processes, which is the mechanism reason for the great difference in the hot spot on the water surface compared with the direct navigation condition. This paper mainly explores the causes of arc-shaped hot spots on water surface, so multiple examples are not used. In response to your question about how to adjust rotating motion to reduce thermal wake, the area of abnormal water surface temperature can be reduced by reducing the radius of rotation, and the peak temperature of abnormal water surface temperature can be reduced by reducing the discharge temperature of cooling water.
2. The grid independence has been verified again.

The underwater vehicle was rotated for 30 seconds, and four sets of total grids with the number of units varying from 4.45 million, 5.45 million, 6.45 million and 7.45 million were adopted. The YZ section of 0.3m behind the body at the initial position of the underwater vehicle was selected. Figure 4 shows the change of thermal wake center temperature on the section with the density of the grid. It can be seen that when the number of grids is greater than 6.45 million, the calculated thermal wake center temperature of cross-section will no longer change significantly with the increase of the number of grids, satisfying the grid-independent condition.

3. The syntax errors have been corrected
4. Grammar errors have been corrected
5. In Figure14, in order to clearly compare the floating position and diffusion range of thermal wake at different sections behind the underwater vehicle, the interception range of thermal wake in the previous five figures remains the same. However, with the distance from the body, the floating and diffusion range of thermal wake along the X direction and the Y direction becomes wider. Therefore, the interception range of thermal wake in Figure (f) is expanded, and the Y-direction size of the picture is reduced to facilitate comparison with the previous five figures.
6. Grammar errors have been corrected.
7. The references have been supplemented and improved and the format modified.

Finally, I would like to express my thanks again for your guidance, and thank you for reviewing and revising my revised paper again. I hope that I can complete an excellent paper with your guidance and help, and sincerely hope that my paper can be published in your journal.

Author Response File: Author Response.pdf

Reviewer 2 Report

Recommendations:

1-Regarding the Mathematical Formulation sections: appropriate references should be presented for some equations.
2- I need clarification on the application of the problem studied.
3-      The Introduction section should include a proper application regarding the present problem.

4-      In the same section, the authors may include more discussions regarding mentioned previous works.
5- There are many grammar and typo mistakes throughout the manuscript. The authors should revise the entire paper carefully before considering it for publication.

6. The literature review can be updated considering recent studies

https://doi.org/10.1007/s13369-020-05195-x

https://doi.org/10.1007/s13369-021-06092-7

https://doi.org/10.1007/s13369-021-06412-x

https://doi.org/10.1140/epjp/s13360-020-00606-2

https://doi.org/10.1080/17455030.2022.2050441

https://doi.org/10.1088/1402-4896/ac03de

DOI: 10.1177/09544089211072715

DOI: 10.1177/09544089221105932

https://doi.org/10.1080/17455030.2022.2072536

DOI: 10.1177/09544089221139696

https://doi.org/10.1080/17455030.2022.2100004

 

 

Author Response

Dear reviewers and editors,

First of all, thank you very much for taking time out of your busy schedule to read and revise my article. I have carefully studied the reviewer's valuable comments and made the following modifications one by one according to the suggestions:

1. The k equation of turbulent kinetic energy and the ε equation of specific dissipation rate have been explained.
2. The research question of the paper has been modified. When the submarine is sailing, most of the heat generated by the nuclear reactor will be released into the sea water, creating a hard to disappear behind the body of the thermal wake, the thermal wake rises to the surface of the ocean to form a hot spot. With the development of infrared submarine exploration technology in the military field, the temperature difference of 0.001℃ on the ocean surface can be detected, which undoubtedly greatly reduces the concealment of submarine. In this paper, the overlapping grid technology will be used to carry out numerical simulation research of underwater vehicle rotating motion in uniform fresh water, explore the mechanism of thermal wake floating and diffusion under rotating motion, analyze the influence of rotary motion on the surface temperature anomaly area caused by thermal wake, and provide theoretical research ideas for reducing the risk of submarine infrared detection.
3. The purpose of this paper is to explore the mechanism of thermal wake floating and diffusion of underwater vehicles, and to provide theoretical research ideas for reducing the risk of submarine being detected by infrared so as to improve the concealment of submarine, rather than proposing new applications.
4. The grammar and typos of the paper have been revised.
5. The references of the paper have been updated.

Finally, I would like to express my thanks again for your guidance, and thank you for reviewing and revising my revised paper again. I hope that I can complete an excellent paper with your guidance and help, and sincerely hope that my paper can be published in your journal.

Author Response File: Author Response.pdf

Reviewer 3 Report

The following minor revisions should be done for publication.

1.       The objective of the study is good for publication.

2.       In mathematical model section, the governing equations must be cited.

3.       Why do you select angular velocity of 0.0524 rad/s, rotation radius 3.82? Is this values state the real life value?

4.       Why do you prefer Realizable k - ԑ turbulence model?

5.       Please add uncertainity analysis for the used experimental equipment.

 

6.       The paper of the title can be modified.

 

Author Response

Dear reviewers and editors,

First of all, thank you very much for taking time out of your busy schedule to read and revise my article. I have carefully studied the reviewer's valuable comments and made the following modifications one by one according to the suggestions:

1. The research purpose of the paper has been modified. In this paper, the overlapping grid technology will be used to carry out numerical simulation research of underwater vehicle rotating motion in uniform fresh water, explore the mechanism of thermal wake floating and diffusion under rotating motion, analyze the influence of rotary motion on the surface temperature anomaly area caused by thermal wake, and provide theoretical research ideas for reducing the risk of underwater vehicle being detected by infrared.
2. Governing equations such as mass conservation equation, momentum conservation equation, energy conservation equation, turbulent kinetic energy equation and turbulent dissipation rate equation have been used in the mathematical model.
3. The underwater vehicle model adopted in this paper is obtained by scaling according to SUBOFF model. The scaling size is 1:90, the scaling ratio of rotation velocity is 0.2m/s, and the corresponding angular velocity and rotation radius are obtained according to the rotation time is 60s.
4. The thermal wake studied in this paper is essentially a circular discharge hot jet and a rotating flow. Realizable k - ԑ turbulence model applicable to jet,, rotating flow, strong curvature of a circular jet flow, and the model has good convergence, consuming less computer memory, so using the model.
5. The thermal wake experiment platform of underwater vehicle was built in this paper, and there were some errors between the surface temperature field obtained from the experiment and the simulation results. The analysis was caused by two reasons: first, weak temperature stratification existed in the experimental pool; second, the underwater vehicle discharged cooling water and destroyed temperature stratification, which would have an impact on the next experiment. Therefore, the water body of the sink should be replaced in time, and the temperature measuring system of the pool fixed array should be used to wait for the experimental pool to be stable before the experiment.

Finally, I would like to express my thanks again for your guidance, and thank you for reviewing and revising my revised paper again. I hope that I can complete an excellent paper with your guidance and help, and sincerely hope that my paper can be published in your journal.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

After review it, I think it can publish in this journal.