Aerodynamic Drag Reduction and Optimization of MIRA Model Based on Plasma Actuator

Round 1

Reviewer 1 Report

The authors investigated numerically the aerodynamic drag reduction and optimization of a vehicle model by plasma actuators.

They focused on the plasma active flow control technology to improve the flow field structure of the vehicle tail.

They found that the maximum drag coefficient using an efficient global optimization algorithm is reduced by 13.17%.

The study is well conducted and the data is presented clearly. The application of plasma actuators for a vehicle will be of interest to readers of this Journal, Actuators.

I have the following concerns.

(1) Please review your English thoroughly. For example, in abstract,

Line 24, “Observe the control effect ...”

Line 27, “And obtain the driving ...”

are incomplete sentences.

Also, Line 30, “will” should be removed.

Through the whole text, a lot of “space” after comma “,”, period“.” and semicolon “;” are missing.

I strongly recommend that your paper will be checked by a native speaker of English.

(2) I think the authors should refer to other similar studies in the introduction.

For example,

Bulletin of the JSME, Mechanical Engineering Letters, Vol. 5, 2019.

“Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator” by Shimizu et al.

https://www.jstage.jst.go.jp/article/mel/5/0/5_19-00354/_pdf/-char/ja

(3) Regarding Figure 3, some information about the actual dimensions of the MIRA vehicle model used in this study should be included. For example, vehicle length, wide, height in meter (or millimeter) unit. Due to the lack of the information, I could not understand the position of “x=0.6m” in Figures 10, 12 and 13.

(4) Line 254, supply voltage is selected between 5000 V and 25000 V. Is this voltage amplitude value or peak-to-peak value?

(5) Line 343-348 and Line 356-361 are duplicative same paragraph.

(6) In Figure 9, the most effective position is D, however in Figure 15, the most sensitive position is C. Could you describe the reason of the difference?

(7) Figure 13, please change the contour legend to lower position because the lower part of “BC” is hidden.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Check the pdf file attached.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments for the authors

In this manuscript, the authors discussed the reduction of the aerodynamic drag around the simple vehicle model using plasma actuators via simulations. The Shyy model was used to apply the effect of plasma actuators on the flow field. Four locations for installing plasma actuators were selected. First, the drag-reduction performance and flow field behind the vehicle model were compared between the four locations. Then, combinations of multiple actuators were applied and compared. Finally, the Kriging-model-based optimization was performed with the voltage of each plasma actuator as a parameter to find the optimum combination for drag reduction.

 This topic is of great interest, and the reviewer thinks the analysis combined with the optimization method is good. However, a major revision of the manuscript is needed before it can be accepted for publication in Actuators.

• The main problem is the lack of validation of the Shyy model. Shyy et al.'s Work validated their model and calculation by comparing velocity profiles with the experimental results shown in Roth's Work, however, the range of voltage was a few kV. Since the voltage selected in this manuscript is much higher than that in Shyy et al.'s Work, it is doubtful whether their validation can be applied to this manuscript. The reviewer thinks that the important thing is whether the magnitude of the induced flow generated by this model is a realistic value or not. In general, the stronger the induced velocity from a plasma actuator is, the stronger the flow-control effect tends to be. However, if the force is unrealistic, the obtained results will be of less engineering significance. Therefore, the reviewer strongly recommends the authors to verify whether the induced flow generated by the Shyy model is realistic compared to several experiments.
• The current introduction is not suitable as an introduction to this manuscript. First of all, this manuscript focuses on the drag reduction of the vehicle model, so the literature survey on it should be increased. Certainly, as the authors have pointed out, there are few examples of installing plasma actuators in vehicle body models. However, there are research works on the Ahmed model and some simple vehicle models as shown below, so it is recommended to refer to them as well.

Boucinha, V., Weber, R., & Kourta, A. (2011). Drag reduction of a 3D bluff body using plasma actuators. International Journal of Aerodynamics, 1(3-4), 262-281.

Shadmani, S., Mojtaba, M., Mojtaba Mousavi Nainiyan, S., Mirzaei, M., Ghasemiasl, R., & Pouryoussefi, S. G. (2018). Experimental investigation of flow control over an Ahmed body using DBD plasma actuator. Journal of Applied Fluid Mechanics, 11(5), 1267-1276.

SHIMIZU, K., NAKASHIMA, T., SEKIMOTO, S., FUJII, K., HIRAOKA, T., NAKAMURA, Y., ... & TSUBOKURA, M. (2019). Aerodynamic drag reduction of a simplified vehicle model by promoting flow separation using plasma actuator. Mechanical Engineering Letters, 5, 19-00354.

Also, before mentioning the Motivation in the final paragraph, the authors explained details of a plasma actuator including a nano-second pulse plasma actuator for two paragraphs. However, the reviewer does not think these relate to the mainstream of this manuscript. The current structure of the introduction is difficult to understand for readers, so it is strongly recommended to restructure.

• Overall, the parameter description is missing. For example, for the body force, the values of all parameters should be given as in p. 6438 in the Shyy et al.'s work.
• The written language and use of grammar require substantial improvement, especially in Section 4. The authors are advised to make a thorough language revision of the manuscript and perhaps have it proof-read by a native English speaker.

Below are minor comments

• Some reference orders are strange, such as Ref[20] at line 70. Please check.
• Line 80: What does the "energy coupling mechanism" mean?
• Line 152: What is the "symmetric wall condition"? What physical values are treated as symmetric?
• Section 2.4: It is better to show the direction of the induced flow of the plasma actuator.
• (5): What are Φ and φ?
• Section 4: The reviewer recommends figuring out the detail of the original flow field at the beginning of Section 4. This will help readers understand the following parts.
• Section 4.1 and 4.2: There is a sense of incongruity that only these two titles are sentences. The reviewer suggests changing them to nouns.
• Line 273: The reviewer is curious about how important the uniformity of distribution is in flow control.
• Line 289: Where is x=0.6m in Fig. 3?
• Figure 11: For clarity, the reviewer recommends drawing the reference line from the original case or changing the vertical axis to the difference of Cd.
• Figure 12 and 13: The authors mentioned "From the histogram, we can also get an interesting information that the application of actuation at both A and B has a very good effect on drag reduction. Conversely, applying actuation at only one of them will increase the drag coefficient.", however only the case of BC, in which the drag coefficients dramatically increased, was focused in flow-field visualizations. The reviewer is really curious about the comparison of AB, A, and B.The reviewer believes that this comparison is useful for understanding the drag-reduction mechanism.
• Figure 14: In Fig. 10-13, the pressure distributions at X=0.6 were shown. Why the surface pressure was visualized only in Fig. 14? Surface pressure directly relates to drag force so the reviewer is curious about surface-pressure visualizing in other cases.
• Line 343-348: The reviewer considers that the ABCD and the optimal are quite different like between the original and the ABCD. What causes this difference? The reviewer suggests the authors clarify this point.
• Line 356-361: The same contents as Line 343-348 are presented. Please delete it.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I confirmed the corrections.

Reviewer 2 Report

Dear authors,

Thank you for considering my sugestions, I believe you have done an excellent work and the quality of the paper was significantly increase. I believe the paper may be accepted as it is.

Reviewer 3 Report

I confirmed that the manuscript has been improved for publication in Actuators.