Numerical Investigation on Aerodynamics of a Rectangular Blade Rotor under Mars Air Conditions Using Large Eddy Simulation
Round 1
Reviewer 1 Report
Manuscript Number: Applsci-2112805
Full Title: Numerical Investigation on Aerodynamics of a Rectangular Blade Rotor under Mars Air Conditions using Large Eddy Simulation
I – General Comments
The present manuscript numerically investigates the aerodynamic performance of a rotor with rectangular blades under ultra-low density Martian air conditions. As support, there is an experimental data base from a Mars Air Simulator (MAS) too. The numerical approach utilizes a Large Eddy Simulation solver, in which the influence of test bench and MAS chamber is investigated through flow field analysis. In general, the results show lift prediction in a very good accuracy, however, the torque prediction is not so promising. There are recommendations/questions addressed to the authors, before to accept their manuscript as Applied Science’s paper.
II - Specific Comments
(i) In “Abstract”, the main contribution of the present work must be better clarified and the present state of the art concerning the investigated topic must also be introduced and contextualized.
(ii) In “Introduction”, the authors did not cite previous works early published in Applied Sciences. Why? Are there other publications about the research topic in Applied Sciences? That key point needs to be clarified by authors to justify their publication. It is recommended an introduction, including justification, of the adopted methodology too.
(iii) In “Section 2”, the authors must clarify the assumed hypotheses for the mathematical formulation including the corresponding justifications. The manuscript is poor in terms of mathematical formulation, since governing equation and boundary conditions have not been included into the technical discussions.
(iv) When stating “Section 2”, a figure illustrating the investigated problem is also welcome aiming to support the comments from topic (iii) above presented.
(v) Please, make sure as the local energy is dissipated for any point of the flow field. How could be associated the concepts of turbulent viscosity (local concept) and the kinematics viscosity (global concept) according the present methodology?
(vi) In “sub-section 2.2”, if the authors utilize a numerical method, it is important to include some explanation about implementation of the present method algorithm.
(vii) Equation 9 needs to be introduced into the manuscript.
(viii) The compressible flow and Mach number (at high speed) concepts must be better contextualized by authors.
(ix) What is the measurement uncertainty of the (experimental) data used as support? See, for instance, Figure 4.
(x) Figure 4 should be broken in 4(a) and 4(b) too. Please, give that same treatment for other figures, when necessary.
(xi) Figure 5 must be better introduced and discussed.
(xii) Is it possible to present Figure 9 in terms of vorticity field? Please, particularly (here) explain/justify the hypothesis of isothermal flow.
(xiii) In “Section 5”, it is interesting to present some comment with respect the present numerical results behaviour as compared as previous/experimental works; so, the contribution of present manuscript can be identified by interested readers. It is also interesting the authors observe that the use of Lagrangian description to alternatively simulate the same problem is very suitable. The meshless approach is interesting for the solution of present problem! And two papers recently published in MDPI system can be cited by authors as reference (including some short comment), i.e.:
[1] https://doi.org/10.3390/fluids6120460
[2] https://doi.org/10.3390/en14248237
In closing, it is important to complement the manuscript with perspectives for a future research.
III - Recommendation for the Applied Sciences´ Editor
In my opinion, the present manuscript needs attend all topics above presented. Upon consideration of all points above, I think the paper could be considered for publication in Applied Sciences.
Author Response
Dear Reviewer,
Thank you for giving so much insightful suggestions, the manuscript has been modified significantly as required. Details of revision are seen in the attachment. Our response may not be perfect because we are on Chinese New vacation, if needed, please don't hesitate to contact us.
Response to Reviewer 1 Comments
Point 1: In “Abstract”, the main contribution of the present work must be better clarified and the present state of the art concerning the investigated topic must also be introduced and contextualized.
Response 1: The “Abstract” is enriched as required and marked in yellow.
Point 2: In “Introduction”, the authors did not cite previous works early published in Applied Sciences. Why? Are there other publications about the research topic in Applied Sciences? That key point needs to be clarified by authors to justify their publication. It is recommended an introduction, including justification, of the adopted methodology too.
Response 2: we have search papers on Applied Sciences, but failed to find related works on the topic of our study. So I cited a paper also using LES for flow simulation. The Introduction is enriched with methodology introduction and justification as required, marked yellow in Introduction.
Point 3: In “Section 2”, the authors must clarify the assumed hypotheses for the mathematical formulation including the corresponding justifications. The manuscript is poor in terms of mathematical formulation, since governing equation and boundary conditions have not been included into the technical discussions.
Response 3: Section is totally reorganized and reconstructed, with governing equations and boundary conditions given in detail.
Point 4: When stating “Section 2”, a figure illustrating the investigated problem is also welcome aiming to support the comments from topic (iii) above presented.
Response 4: the investigated problem is re-depicted in the new Section 2. Since we are in the Chinese New Year vacation (like Christmas in west), we didn’t have enough time to construct a proper figure for this. If necessary, we will do this in the next round.
Point 5: Please, make sure as the local energy is dissipated for any point of the flow field. How could be associated the concepts of turbulent viscosity (local concept) and the kinematics viscosity (global concept) according the present methodology?
Point 6: In “sub-section 2.2”, if the authors utilize a numerical method, it is important to include some explanation about implementation of the present method algorithm.
Response 5&6: the concerns are resolved in the new Section 2, please see in the methodology part.
Point 7: Equation 9 needs to be introduced into the manuscript.
Response 7: Equation (9) (now Equation (19) ) has been introduced and marked in yellow in section 3.
Point 8:The compressible flow and Mach number (at high speed) concepts must be better contextualized by authors.
Response 8: the compressible flow and Mach Number concerns related to the research are contextualized in Section 2.2, marked in yellow.
Point 9:What is the measurement uncertainty of the (experimental) data used as support? See, for instance, Figure 4.
Response 9: the uncertainty is discussed in Section 4.1, marked in yellow.
Point 10:Figure 4 should be broken in 4(a) and 4(b) too. Please, give that same treatment for other figures, when necessary.
Response 10: the related figures have all been treated as required.
Point 11: Figure 5 must be better introduced and discussed.
Response 11: Figure 5 is further discussed in Section 4.2, marked in yellow.
Point 12: Is it possible to present Figure 9 in terms of vorticity field? Please, particularly (here) explain/justify the hypothesis of isothermal flow.
Response 12: A new Figure on vorticity field is added and discussed in Section 4.4, marked in yellow.
Point 13: In “Section 5”, it is interesting to present some comment with respect the present numerical results behaviour as compared as previous/experimental works; so, the contribution of present manuscript can be identified by interested readers. It is also interesting the authors observe that the use of Lagrangian description to alternatively simulate the same problem is very suitable. The meshless approach is interesting for the solution of present problem! And two papers recently published in MDPI system can be cited by authors as reference (including some short comment), i.e.:
[1] https://doi.org/10.3390/fluids6120460
[2] https://doi.org/10.3390/en14248237
Response 13: thanks for providing fresh ideas, we are sorry that we didn’t have enough time for further investigation on new reference due to the Chinese New Year vacation. If necessary, we will do this in the next round.
Point 14: In closing, it is important to complement the manuscript with perspectives for a future research..
Response 14: the perspectives for future research are added in Section 4.2, 4.4 and Conclusions.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This manuscript discusses the aerodynamic performance of a rotor with rectangular blades under ultra-low-density Martian air conditions. The authors perform LES with WALE subgrid model. The structure of the paper is extremely disappointing. The numerical methodology presented is incomplete. There is no validation of the results. The information on the energy spectra and filter size have not been provided. Mesh and Time step independence are missing. The results are extremely vague and mostly do not address the critical issues of aerodynamic performance. It is hard to follow contours and streamlines devoid of any meaningful information e.g. figures 5, 8, and 9. This paper does not meet the publication standards of any decent journal. Therefore, this paper must be rejected.
Author Response
Dear Reviewer,
Thank you for reviewing our paper and giving advices. The manuscript has been reorganized and constructed. Please give us more adivces.
Best wishes!
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Manuscript Number: Applsci-2112805-v2
Full Title: Numerical Investigation on Aerodynamics of a Rectangular Blade Rotor under Mars Air Conditions using Large Eddy Simulation
The original text of the manuscript has been satisfactory revised. So, the present manuscript can be published as an Applied Science’s paper.
Reviewer 2 Report
The authors have improved the manuscript significantly and therefore it can be accepted for publication.
