Study on Nonlinear Correlation in Modal Coefficients of the Bionic Airfoil

Round 1

Reviewer 1 Report

The authors present a neat paper regarding nonlinear correlation in modal coffeicients for different airfoils.

While the numerical approach seems sound, the paper could use a deeper description of the actual physical phenomena the mathematical model is supposed do model. For example, at the low Re investigated, is it acertained that the NACA4412 will develop a trailing edge separation and not a LE laminar bubble burst?
Also, the selection of the NACA4412 needs to be more thouroughly motivated as it is an older, an in all honesty not a very good airfoil.
Figure 3 shows a difference of Max CL alpha of about 2 degrees - Im not sure that could be called a good agreement, something is a bit off here.

The language needs another read through. The sentence starting on row 28 "Phenomena..." is not complete.
Row 98 "Maximum radian" should it be "maximum camber"?

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The abstract does not provide na appropriate overview of the study. For instance, there is no mention of a numerical study in the abstract. I was not able to find any grid independency study (mandatory for any numerical study) in the manuscript, which invalidates all the obtained results. Moreover there are no governing equations given in the manuscript, so it is not possible to know was is being simulated. Lastly, there are no details regarding the numerical discretization schemes of the different variables, under-relaxation and so on. For these reasons I am not able to recommend the manuscript’s publication.

Detailed comments:

Line 27-28: “which will cause airfoil stalls starting at low wind speeds and running at high wind speeds.” Could the authors develop on this sentence?

Line 28-29: “Phenomena such as boundary layer separation on the airfoil surface.” This sentence is not connected to the rest of the texto

Line 29: “These unfavorable fac-tors…” Which factos?

The first paragraph in the introduction needs to be rewritten since there are sentences out of contexto and aplications introduced ad hoc without na explanation.

There is a need to define what is a bionic airfoil

Avoid using acronyms in the abstract

Line 71: “Callaham et al. [32] were striking”, dos not make sense; rewrite to proper english

Line 99: “ chord length after dimensionless”, rewrite to proper english

What do the S and A coefficients represente physically?

Line 106: “maximum radian”, what does it mean?

Where is the grid independency study? There are no governing equations in the manuscript. How are the diferente variables discretized? Since this is na unsteady study there i salso a need to demonstrate the results’ Independence from the time step.

Line 154-155: ”… which proves that the numerical simulation of the two-dimensional airfoil in this study is compelling and reliable.” Given that no grid independency study is given, the validity of the results cannot be demonstrated.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

After going through the revised manuscript, there is still information missing regarding the numerical setup which would allow for the results to be reproduced, namely, how were the advective and diffusive fluxes in the governing equations discretized?

Another this I do not understand is why in the governing equations, the Reynolds average and fluctuations only appear in some of the terms.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

The authors addressed some issues raised during the review process. However, I still believe the quality of the presentation is low and , as a result, some interesting aspects of the work carried out are lost.