URANS Analysis of a Launch Vehicle Aero-Acoustic Environment

Round 1

Reviewer 1 Report

The paper discusses the modeling of the noise emitted by rocket during take-off
The software type should be specified if commercial or written in hause.

If the software is commercial it is the theoretical application and this makes the paper weak.

2 3.1. Validation of results
this paragraph should be rewritten and understand how you performed the validation test. This is the gist of your paper. The test case checks your model.
But do you only have one test case?
How were the acoustic measurements performed?
With what microphones? With what system?
Can you give an idea of ​​the measured dB?
How does sound propagate into the surrounding terrain?
Can there be potential harm to people?
On this part your paper should be described more.

Explain better how you performed the model and how you got the results. Lacking the speimantel verification of your simulation each number could be right, but also wrong.
You should make it clear that your model gives correct results
Improve image quality.
I think the paper is interesting considering that missile launches have increased to send commercial satellites into space.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors present an aero-acusitc investigation of a VEGA roket start event. The main goal is the identification of sound sources, which (I guess) should be used to reduce starting noise. The paper first discusses the observed noise sources and shortly discusses the model before presenting results.

The following points have to be addressed before the manuscript is suitable for publication:

• Languange - there are several typos and grammar issues, e.g. Line 26: "Ah shown in Figure 1b...", or Line 112: "There is not readily available data in the exhaust gases vicinity for the CFD..."
• Several model simplifications are discussed in the introduction, referring to literature but without citing relevant sources L47-54
• Section 2.1: it would be nice to have a short introduction to the used model and refer to [8] for the details. Otherwise, it is impossible to understand what is actually done.
• L81: What do you mean by "the  mean velocity is the same value"?
• L87: What is meant by "every fluid magnitude"? Do you mean fluctuations in all directions?
• Section 2.2 how does the used mesh compare to the ones created for the mesh study?
• Fig. 3:
  • Please place Figure 3 in between paragraphs - currently, it intersects a sentence
  • Captions are redundant, please reconsider them
• L120 - 130: I am a bit lost in this paragraph - please rephrase it to make it more understandable
• Fig. 4:
  • There is an issue with the captions
  • It shouldn't be placed directly after a sub-heading
  • Why are the contour plots in Fig. 4a rotated?
• Fig. 5:
  • Why are the individual contour plots rotated?
  • Could you please increase the size of the sub figures - it is very hard to see the details
• Fig. 6:
  
  • I'm lost with this figure - what exactly is shown in panel a?
  • Pannels b and c show the temporal pressure evolution at specific height for different azimuthal positions, is this correct?
  • Increase the size of the figures to improve their comprehensibility
• L174: Do you mean Fig 6 instead of Fig 5?
• L177: "It should also be..." instead of "Also, it should be..."
• L179 - 188: Please improve this paragraph - currently it is hard to understand
• L187: what do you mean with directive? Do you mean the direction?
• General points:
  • which CFD code did you use? This is never mentioned in the manuscript
  • I think some parts, especially the introduction, could need some additional references to provide a sound discussion.

 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

In the paper there is no reference to dB (sound pressure level). It should perhaps be contextualized to dB, or to dBA.
A comment on this lack should be made.
The methodologies of how the experimental comparison measurements were performed are not reported. The paper should be extended to understand the sound levels expressed in dB or dBA

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

please find my comments to your answers below:

1. L112 is still exactly the same, now L121 - what about rephrasing it to "Measurement data to validate CFD models is scarce in the vicinity of the exhaust gases." ?
2. No comment
3. I've checked ref. 13 - as far as I found out it is not open-source, which means that anybody who lacks a subscription to the specific journal is not able to reproduce/understand the presented results. That's why a short model description should be included.
4. Maybe rephrasing this sentence makes it less confusing - one way could be "The time-averaged average velocity is equal to the average velocity by definition." (correct me if I'm wrong)
5. From your explanation I think you mean scales instead of magnitude - if I'm correct, you could rephrase the second part of the sentence to something like "..., takes into account fluctuations at resolved and non-resolved scales."
6. No comment
7. No comment
8. No comment
9. Better now
10. Clear now, maybe also mention in the manuscript, if they are still rotated (doesn't look so)
11. Clear now, maybe also mention in the manuscript, if they are still rotated (doesn't look so)
12. Got it now
13. No comment
14. No comment
15. No comment
16. No comment
17. Thanks for answering

Other than these comments, I've found a few minor things:

• Caption Fig 1.: space between a)S and b)S missing
• L90: shouldn't it read Equation 1 instead of equations 1?
• Fig 4: sub-subcaptions as 4aa or 4ab might be missleading - why not 4a - c?
• L194: Figure 6 b) ad c) - I assume "ad" should be "and"?
• L206: which magnitude is refered to? Pressure or velocity? please specify
• Fig 6: sub-figure labeling in the caption might be a bit missleading for b)
• Fig 7: space missing between a)G

 

Author Response

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Author Response File: Author Response.docx