Study on Oscillatory and Undulatory Motion of Robotic Fish
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
1. An interesting numerical study of fish oscillatory and undulatory motions in Ansys is presented. This is a numerically demanding task, yet interesting results are presented.
2. Page 3, lines 107-108: The rationale for selecting the velocity field given by Eqs. (1)-(3) is required:
a) How have you obtained the expressions in Eqs. (1)-(3)?
b) Could you please present the plots of those velocity fields in the $xyt$ coordination frame to let the Readers understand the shape?
c) Explain symbol $\theta$ in Eq. (1).
d) How do you define the positions $x$ and $y$? Are these the positions of mesh nodes?
e) How do you define the angular amplitude $\omega$? Is this the angular speed of the mesh nodes? Please explain this quantity in a figure.
3. Page 4, lines 136-137: The rationale for selecting the grid motion given by Eqs. (4)-(5) is required:
a) How have you obtained the expressions in Eqs. (4)-(5)?
b) Could you please present the plots of those grid motion fields in the $xyt$ coordination frame to let the Readers understand the shape?
4. Page 5, line 148-149: Please explain the quantities in Eq. (8) - what is $\nu$ and what is $\nu_t$?
5. Page 5, line 170: "The values of these constants have been arrived at by numerous iterations of data fitting for a wide range of turbulent flows." - Could you please give more details about those "numerous iterations of data fitting":
a) Which data was fitted to what?
b) What turbulent flows where considered?
c) What shapes/objects were analyzed?
6. Page 6, lines 198-204: The selection of the unstructured mesh in the vicinity of the swimming object is unclear.
7. Page 7, lines 221-222: Please give exact values for the following quantities in Tab. 1: Outlet/Prescribed pressure and Fish surface/Prescribed velocity.
8. Page 9, lines 270-271: "... the observed results from both the experimental and numerical methods are different." - Please explain how the experimental data was obtained. What kind of experiment was performed? What measurement equipment was used? Please give photos of this equipment, etc.
Comments on the Quality of English Language
The language of the paper is rather correct.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsSome suggestions:
1. Study how to optimize motion control when simulating in an ideal environment, taking into account practical factors such as water flow and obstacles.
2. The resistance variation trend of the model varies at different frequencies and flow velocities. How to achieve maximum thrust under different conditions (perhaps the best flow velocity and frequency can be obtained through reinforcement learning).
3. Under shallow and deep water conditions, due to changes in the ratio of draft to depth and the presence of shallow water effects, hydrodynamic characteristics will undergo significant changes. What are the changes in fluid dynamics characteristics under different water depth conditions.
What are the advantages and disadvantages of the robotic fish model compared to traditional underwater vehicles in terms of propulsion efficiency and motion control, and what improvements can be provided for traditional underwater vehicles.
5. Real aquatic organisms can eliminate rolling moment, yaw moment, etc. by adjusting the angle of attack of the body towards the water flow and utilizing the interaction of the tail fins, dorsal fins, and pectoral fins on the body. How to achieve this on artificial robotic fish.
Comments on the Quality of English LanguageMinor editing of English language required.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe topic of the manuscript is interesting. Nonetheless, there are a few issues that ought to be taken into consideration:
1. What are the schemes that you used for the discretization of the convective and diffusive terms? What are the schemes that are used for the discretization of temporal terms? The authors also need to clarify the order of accuracy of each scheme that they use.
2. Please provide pictures or quotations related to the experiment to enhance persuasion.
3. Please provide the corresponding figure numbers for the descriptions in the paragraphs of the manuscript.
4. Please appropriately add references from the past 5 years.
Comments on the Quality of English Language
I recommend that the authors have their manuscript revised by an English native speaker.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
The Authors have addressed most of my previous comments and introduced specific corrections in the text. In their response the Authors have attached the code snippets as well as new figures, which clear most previous points. However, the last point is still unclear: in Fig. 10 there is still "experimental", not "theoretical". Moreover, it is still unclear how the "theoretical" results have been obtained For the detailed new comments see below.
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Previous comment 2. ...The rationale for selecting the velocity field given by Eqs. (1)-(3) is required...
New comment 2. Thank you for the explanations and for the correction in the text.
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Previous comment 3. ... The rationale for selecting the grid motion given by Eqs. (4)-(5) is required...
New comment 3. Thank you for the explanations.
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Previous comment 4. ...Please explain the quantities in Eq. (8)...
New comment 4. Thank you for the explanations and for the corrections in the text.
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Previous comment 5. ...Could you please give more details about those "numerous iterations of data fitting"...
New comment 5. Thank you for the explanations.
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Previous comment 6. ...The selection of the unstructured mesh ... is unclear...
New comment 6. Thank you for the explanations.
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Previous comment 7. ... Please give exact values for the ... quantities in Tab. 1....
New comment 7. Thank you for the explanations. I did not catch the quantity meanings previously.
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Previous comment 8. ... Please explain how the experimental data was obtained...
New comment 8. The Authors have changed "experimental" to "theoretical" in most phrases in lines 271-284. However, in Fig. 10 there is still "experimental", not "theoretical". Moreover, it is still unclear how the "theoretical" results have been obtained. What "theoretical" calculations have been performed to obtain the data in Tab. 3 and in Fig. 10? This is a serious point, and without the explanation, Tab. 3 and Fig. 10 should be removed, and the Authors results cannot be verified.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have polished the paper very carefully according to the reviews. The paper is ready for publication now in my viewpoint.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
