Comments on abstract, title, references

The paper focuses on an interesting topic of aerodynamic lift force enhancement using two different kinds of airfoil. It contains interesting results; however, the paper has to be basically modified before publication in a journal.

• The title is not explicitly stated, so it is suggested to be more precise, so the term "comparison" has to be specified in the title if it means a comparison between two airfoils or two methods.
• The key conclusions are not well identified in the abstract and any enhancement in the lift force needs to be highlighted.
• No up to date references have been considered and there are many papers discussing the airfoils shape to enhance the aerodynamic performance in recent two to four years… Pleased add up to date papers
• References style needs to be more integrated

Comments on introduction/background

• The author claimed in the introduction that “The goal in this work focuses on presenting a description of the physics of flow in response to the enhancement of lift and elimination of the drag” This is not new or novel aspect as several researches have tried to eliminate the flow separation using different kind of flow control techniques such as vortex generator, synthetic jet actuators, and plasma jet actuator etc.

• Most of the text included is reviewed others work and no contribution or aim and objectives can be seen.

• "Literature Review" presents some information in a misleading manner. For example, the author/s reviewed how the aerodynamic performance can be improved when the airfoil is modified in different manner which could be true under specific conditions parameters and constraints. In fact, a change of arbitrary airfoil shape can cause either an increase or a decrease of the aerodynamic performance. A combination of the specific conditions, parameters and constraints cause that the resulting effect is increasing or decreasing in character. Vague generalization and misleading wording cannot be used in a scientific paper. -

Comments on methodology

• The methodology section is strangely restricted to Fluent applications (numerical simulation) and there is no specific details about the manufactured configuration for the experimental setup, and this contradicts what was suggested in the aim.
• Figure 2 displays just the unsymmetric model, while missing the symmetric one
• As mentioned (in page 4),"CFD simulation the coordinates for NACA 0015 and NACA 4415 of the airfoil is imported and the geometry is created". Unfortunately before the results and discussion section, solution method and mesh independent study need to be clearly considered in the paper. This would help verify if the number of cells was unaffected by the values monitored.
• The author/s need to avoid using “we” “I” etc which reduce the quality of the paper and not accepted in a scientific journal.
• In any numerical simulation, the numerical model needs to be clearly written such as Laminar/ Inviscid or Turbulent models. However, the type of model used is not addressed in the current CFD simulation.

Comments on data and results

• Figures 4 and 5, the static pressure and velocity magnitude are unreadable with meaningful explanation. Moreover, it is not clear whether the whole airfoil has been rotated to change the AOA Or has the direction of inlet velocity been altered?
• The title of Figure 4 and 5 is not clearly showed which is the Contours for NACA 0015 and NACA 4415.
• The results of experimental work in Figure 7 are not clearly where came from? is it from the author himself or others related work?
• Figure 4 and 5 only a vague photo. I suggest rewriting this part in more specific detail and any results change should be described properly.

Comments on discussion and conclusions

• The author stated that "At 18° AOA significant turbulence and flow separation is visualized" but no such information about the onset location and how differ from other airfoils.

• The author claim that "The shape of the stream line indicates a change from a deficit to an excess condition across the vortex core at the leading edge" and however, no such information about the streamline can be seen which this helps to identify the vortex formation more precisely.

• Figure 6 is discussed the pressure coefficient against position of chord length at AOA =6 . Why this AOA is selected in comparison to other important AOA? Hence, another clarification about the cp needs to be included at different AOA.

• The author was compared between Numerical and Experimental data in terms of lift and drag forces. There is no such clarification on the experimental results, though, if it comes from the present research or linked with other similar studies?
• One of the main concerns in Figure 7 is that the lift value is ranged between Cl = 0.15-0.2, this is impossible and I think the author means 1.5-2?
• In conclusion, there is a clear limitation of the study which concentrated on a topic that been discussed too many in literature and hence no significant contribution can be extracted for future work.
• In conclusion, the author claim that "it is clear that the cambered aerofoil NACA 4415 is distinctly the most efficient aerodynamic shape than symmetrical aerofoil NACA 0015". This is something already mentioned in the literature since long time and hence no such innovation to justify.

Overall statement or summary of the article

The authors did a good engineering work but, definitively, there is not so much innovation to justify a full length research article. Also the performed analysis is rather standard and majority of them are available in too many sources . Thus, in my opinion, the authors should re-submit this work in a presentation/report form.

Overall strengths of the article

The paper focuses on an interesting topic of the flow over airfoils. It contains interesting basic numerical results which can a researcher start with. However, an obvious weakness of the paper is an unacceptable.

Specific comments on weaknesses of the article and what could be done to improve it.

This paper presents the results of numerical and experimental studies on the flow over airfoils. The reviewer recognizes that CFD can be a powerful tool for designing airfoils as already demonstrated in previous studies. However, the results presented here is very specific and the results cannot be transferred to universal knowledge. Unfortunately, it is difficult to find its novelty and scientific contributions to the field based on the results presented in the manuscript. My main concerns are as follows: - The title is not explicitly stated, so it is suggested to be more precise, so the term "comparison" has to be specified in the title if it means a comparison between two airfoils or two methods. - The abstract needs to be rewritten with the aim, contribution and main findings clearly seen. - The paper's contribution needs to be explained with the research question written done in the introduction. - The author needs to expand the work further using one of the application of flow control which can improve the paper to be publishable. - The section is strangely limited to Fluent software, while the author claim that the experimental study was conducted? - Solution method and mesh independent study need to be clearly considered in the paper. This would help verify if the number of cells was unaffected by the values monitored.

Minor comments:

• In Figure 4 and 5, It is hard to recognize the resolution from the figures.
• Figure 7 numbers need to be checked against the literature
• The author/s need to avoid using “we” “I” etc which reduce the quality of the paper and not accepted in a scientific journal.
• No up to date references have been considered and there are many papers discussing the airfoils shape to enhance the aerodynamic performance in recent two to four years… Pleased add up to date papers
• References are written carelessly and format of References is very irregular. Therefore, References style needs to be more integrated