Investigation on Surface Roughness of PolyJet-Printed Airfoil Geometries for Small UAV Applications
Round 1
Reviewer 1 Report
However, some concers about the evaluation of aerodynamic coefficients (i.e. CL and CD) require more details about the numerical metodology and results obtained. In particular, the higher roughness increses both CL and CD values (table 4). It should be more argued.
In addition, the sentence at pag. 1 rows 312-324 seems to need additional clarification expecially on higher CL effects on performances.
Finally, it is required to specify if the dimensions of the specimens reported in figure 1 are fully representative of the actual dimension of UAV wing.
A table reporting the main UAV characteristics could help in the readibility of the paper.
Author Response
Thank you for your recommendations and feedbacks. Based on your feedbacks, we prepared a revised version of the paper. Please find our responses to your feedbacks at the attachment. Thank you.
Author Response File: 
Author Response.docx
Reviewer 2 Report
General Comment
In this paper, the authors present their study evaluating the influence of manufacturing parameters on the surface roughness of wing produced using PoliJet. I found the paper very interesting and covering a current research topic. However, from my point of view the paper requires major revisions before being ready for publication.
Comments and Questions
From my point of view, the first time you present X, Y and Z directions (section 1) you should mention what are these directions to help the reader to understand them.
To improve the understanding of the paper, I suggest you to add a paragraph summarizing the layout of the manuscript at the end of section 1.
What is the geometry of the airfoil? Is it a NACA0012?
Why did you only take 3 measurements for each specimen and not more? From my point of view, you should perform more measurements to account for uncertainties in the measuring process. In fact, the results presented in Table 3 show substantial variations for several of the surfaces analyzed, even for those printed horizontally.
Furthermore, why didn’t you manufacture more sample for each specimen? This would be important to evaluate uncertainties in the manufacturing process.
I think you should explain better lines 168 to 180 to make it clearer. From what I understood, you surveyed different small UAVs and them chose a given size and different airspeeds. Is that it?
What kind of internal structure did you used?
What was the range of Reynolds number analyzed?
I suggest you to include a figure illustrating your CFD mesh.
Did you perform a mesh convergence study to evaluate the mesh influence on the results?
Given the fact that you don’t have experimental wind tunnel tests, I would suggest you to run the CFD simulations also with a different turbulent model (e.g. k-ε) to enrich the discussion.
On page 6, you mentioned that “vertically oriented parts showed very high amount of distortions especially in trailing edges due to high aspect ratio and slenderness”. From my point of view, it is rather the small size of the trailing than the high aspect-ratio of the wing. In fact, your wing model doesn’t have a high aspect-ratio (I estimated to be around 3 from table 2).
I would suggest to change Figure 4 to a x-y plot with both CL and Cd to better visualize the linear (CD) and nonlinear (CL) effect mentioned in the text.
Typos
On page 1: line 22, where it reads “%7”, it should read “7%”; lines 34 and 36, where it reads “max. take of”, it should read “maximum take-off” or “max. take-off”; lines 43 and 44, where it reads “unlike from conventional manufacturing”, it should read “unlike conventional manufacturing techniques”.
On page 5, line 164, where it reads “(MAC) is”, I suggest to change it for “(MAC) which is”.
On page 6, line 215, where it reads “was”, it should read “were”.
The journal name in reference 30 seems strange.
Author Response
Thank you for your recommendations and feedbacks. Based on your feedbacks, we prepared a revised version of the paper. Please find our responses to your feedbacks at the attachment. Thank you.
Author Response File: Author Response.docx
Reviewer 3 Report
The authors successfully attempt to investigate the surface roughness characteristics of PolyJet printed airfoil geometries. To reach the conclusions, experimental measurements and CFD analysis in various test cases are conducted and explained thoroughly. The conclusions are very interesting, as is the data acquisition methodology. However, before the manuscript reaches publication, there are some (rather minor) comments that need to be addressed.
- Section 2.2/pp.6 – Please add a couple of figures that describe the mesh used in the analysis, to visually assist reader comprehension.
- When referring to the turbulence models, please be precise. The authors use phrases such as "both models" or "combination of both", which is a bit fuzzy, given the discussion in the previous lines of the manuscript.
- Please rephrase the sentence in lines 322-323, it is rather difficult for the reader to understand its meaning.
- I suggest that the manuscript is proof-read (grammar/syntax/spelling check), preferably by a native English speaker.
Author Response
Thank you for your recommendations and feedbacks. Based on your feedbacks, we prepared a revised version of the paper. Please find our responses to your feedbacks at the attachment. Thank you.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors,
after the improvement, I consider acceptable for pubblication your paper.
Author Response
Thanks for the valuable feedbacks. We implemented all the feedbacks that you suggested.
Author Response File: Author Response.docx
Reviewer 2 Report
I think the paper has been improved by the authors, although there are still some typos.
On page 3, line 131, where it reads “build” it should read “built”.
On page 12, line 321, where it reads “attach” it should read “attack”.
Also on page 12, line 322, where it reads “is displayed” it should read “are displayed”.
On page 12, lines 341 and 354, where it reads “increas” it should read “increase”.
On page 12, line 345, where it reads “increases suddenly 10º” it should read “increases suddenly at 10º”.
Author Response
Dear Sir/Madam,
Thanks for the valuable feedbacks. We implemented all the feedbacks that you suggested.
Author Response File: Author Response.docx
