Two Coupled Analysis Strategies for Melt-Ablation Modeling of Thermal Protection Material in Supersonic Gas-Particle Two-Phase Impingement Flow

Round 1

Reviewer 1 Report

The authors propose a methodology to reproduce the melting and ablation phenomena caused by collisions of two-phase flows containing supersonic dispersive particles by means of loosely coupled simulations. The validity and superiority of this methodology are discussed in comparison with experiments and also with the coupled computational method. This study is considered a worthwhile endeavor because of the complexity of the analysis it achieves. The paper itself is somewhat verbose, especially in the introduction, especially in the review of previous studies, and there are few descriptions of important comparative experiments, and there is room for improvement in the presentation of results.

Therefore, I would like to reconsider the recommendation of the paper publication after the authors’ reviewing and revising the manuscript with addressing the following issues:

 

- In relation to the modeling of the equations of momentum and energy, some non-property values, model constants or functions, are not clearly defined or presented with specific values. It is important to clearly state these functions and values for others to reference or follow-up experiments. For example, the turbulent heat transfer coefficient (L. 298), the turbulent Prandtl number Pr_t (L. 299), Γ_k and Γ_ω (Equations 8 and 9), α^* (Equation 10), turbulent diffusion coefficient D_t (Equation 13), F_other (Equation 14)，etc.

- The specific formulas used in this study should be shown for "user-defined source terms" at Line 318.

- The term of “, respectively” is not required at Line 363, whereas it is needed at Line 358.

- Vector notation such as in Equation (24) is also needed for Equations (20) and (22), and so on. Be sure to reconsider the other equations as well.

- I could not understand “a representative length derived from the face area” at Line 420.

- An explanation is needed for “UDF” at Line 440.

- At Line 483, “see Figure 3” may be “see Figure 2” correctly.

- The absence of any explanation for the top two images in Figure 3 makes them completely uninterpretable.

- The font size in Figure 4 is too small. 

- Often, units are missing. Please check Figure 4, Tables 5 and 6.

- What does “A” and “n” in Table 5 mean? 

- Highlight the melt-ablation zone in Figure 5.

- In Section 2.10.1, isn’t it correct that bullet numbers (1) through (5) are at the beginning of the sentence, not 8 through 12?

- In relation to Figure 6, is there any dependence on the time step? Any verification of that? Indeed, how much were used in this analysis? How does it correspond to the physical phenomenon (time scale)?

- The results of the 3D analysis should be directly compared quantitatively by means of graphs, just as the results of the 2D analysis. That is, a portion or azimuthally averaged values of the top two results in Figure 7 should be shown simultaneously in the bottom graph to encourage rigorous comparison.

- Table 7 would be much better graphed in a figure.

- The absence of any explanation for the bottom two images in Figure 8(a) makes them completely uninterpretable.

- At Lines 768 and 771, what does (b) in Figure 12 mean? Figure 12 shows only one figure. Also, Figure 12 does not work very well, and is better since it is mentioned in the text?

- A final but important comment is that the content of Reference 8, which is the subject of the comparison, should be explained in brief, from the methodology to the main results. This is because the proceedings of the national conference are inaccessible to most people. In fact, I cannot confirm the content of the experiment itself, and I must conclude that the reliability of the experiment cannot be confirmed, and that the validity of the results of this calculation is also essentially unknown.

Author Response

Dear Reviewers,
We appreciate the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.pdf

Reviewer 2 Report

1- The authors should review Figure 8(a) and set correctly the colorbar

2 - For the numerical simulation, what is the excitation ? What is the mesh element size ? is there any mesh convergence criteria ?

3-Indicate some references for equations 4-13

4-Line 768, 771 : there is no Figure 12(b)

Author Response

Dear Reviewers,
We appreciate the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Dear Reviewers,
We appreciate the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors' have responded to all specific points I raised in my report and have accordingly revised their manuscript. The current version is an improvement over the original submission.

 

Regarding my previous Major Comment 1:

in my previous report I wrote that: "In relation to the modeling of the equations of momentum and energy, some non-property values, model constants or functions, are not clearly defined or presented with specific values. It is important to clearly state these functions and values for others to reference or follow-up experiments."

Unfortunately, these points apply equally to the current version.

The authors have claimed that the reader should refer to the software's manual guide, and further stated that they used default values. However, the version of the software is not specified in the manuscript, and the manufacturer's manuals could be updated. The description is very unhelpful to the reader, and it cannot be said with certainty that a similar analysis can be performed. An analysis that cannot be reproduced is problematic for a scientific/academic paper. It seems to me that this is simply negligence on the part of the authors. At the very least, the values given in the review response (Pr_t=0.85, D_t=2.88e-05, Sc_t0.7) should be included in the paper, and it should be clearly stated that the default FLUENT formula was used.

 

Regarding my previous Major Comment 5:

Unfortunately, I have no idea how the authors made the corrections. Therefore, I still do not understand the part (Line 404-405) in question.

Author Response

We appreciate you and the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors should give some descriptions on Lin's experiments and its operational conditions 

Author Response

We appreciate you and the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.docx

Reviewer 3 Report

 

 

I checked the cover letter provided by the authors carefully, and I found that the authors did not reply to my sixth comment, and the response they provided replaced my sixth comment with the fifth comment, that is, the fifth comment was replied twice.

My six comment is “The authors should provide a more detailed description of Lin's experiment in a separate section, including the propellant, components, operational conditions, and measured parameters, to facilitate a corresponding analysis of the subsequent simulation study.”

 

As for my seventh comment, the author has only replied part of it, and there is no corresponding response to the rest.

My seventh comment is “What is the significance of using a 2D axisymmetric model in the article? A simulation model like this does not correspond to any experimental device in reality, and the flow field structure in Lin's experiment is different from that in the 2D axisymmetric model. What is the reference value of the results obtained using 2D axisymmetric calculations? Figure 7 is confusing. In (a), it shows the 3D calculation result without the 'ablation zone', while in (b), it shows the 2D calculation result with the 'ablation zone'. From both the 3D and 2D perspective, the two models are not comparable at all. Additionally, why is the image in Figure 7(b) not axisymmetric since this result is obtained by a 2D axisymmetric calculation?”

 

And the authors only replied to “What is the significance of using a 2D axisymmetric model in the article? A simulation model like this does not correspond to any experimental device in reality, and the flow field structure in Lin's experiment is different from that in the 2D axisymmetric model. What is the reference value of the results obtained using 2D axisymmetric calculations?”

Author Response

We appreciate you and the reviewers for your precious time in reviewing our paper and providing valuable comments. It was your valuable and insightful comments that led to possible improvements in the current version. The authors have carefully considered the comments and tried our best to address every one of them. We hope the manuscript after careful revisions meet your high standards. The authors welcome further constructive comments if any.

Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

no comments