Aerodynamic Modification of High-Rise Buildings by the Adjoint Method

Round 1

Reviewer 1 Report

This study focuses on a novel numerical methodology designed for aerodynamic modification of three-dimensional high-rise building, which combines CFD and the adjoint method. It seems that the golobal forces on the structure have been reduced. However, what are the effects of these mofications on the local extreme wind forces?

The language of the paper presents some errors and imprecisions, and would benefit from a thorough review

Author Response

Dear Editor,

We are very thankful to the positive and valuable comments from the editor and reviewers which expressively improve the quality of this paper. It is our great pleasure to submit the revised version of this manuscript based on the generous suggestions and comments of the reviewers, which we wish could satisfy the editor and reviewers.

Comments and Suggestions for Authors

#Reviewer 1

This study focuses on a novel numerical methodology designed for aerodynamic modification of three-dimensional high-rise building, which combines CFD and the adjoint method. It seems that the golobal forces on the structure have been reduced.

We firstly are grateful for the reviewer’s effort in reviewing our manuscript and the positive comments that acknowledge our paper’s contribution. The following are our replies to each question one by one:

However, what are the effects of these modifications on the local extreme wind forces?

• Thanks for your valuable comment. In this research, we mentioned the local average velocity in different Reynolds numbers and the effect of direction wind velocity forces as an attack angel. So the results are examined in the manuscript and their aerodynamic forces.

Comments on the Quality of English Language

The language of the paper presents some errors and imprecisions, and would benefit from a thorough review

The whole munascript was revised carefully.

Reviewer 2 Report

The manuscript applies the adjoint method to numerically perform a sensitivity analysis and assess the influence of aerodynamic shape on drag forces (CD and CL). While the approach may be effective in adjusting the aerodynamic configuration of tall buildings, the manuscript, at its present form, omits numerous details relating to the CFD simulation and some of the text requires significant improvement. Therefore, this reviewer recommends major revisions.

Specific comments are included below:  

1) The authors mentioned a hybrid RANS/LES CFD solver executed in ANSYS. However, many critical CFD simulation parameters (e.g., coefficients specified in the turbulence models, sub-grid turbulence modeling, etc.) still need to be reported, and only the time step was specified in the manuscript. With the current information, future researchers would be unable to replicate the results.

2) Line 54-55: The authors are missing recent wind tunnel studies directly related at aerodynamic optimization of tall buildings. Some examples are included below:

-Li, Y., Zhu, Y., Chen, F. B., & Li, Q. S. (2023, October). Aerodynamic loads of tapered tall buildings: Insights from wind tunnel test and CFD. In Structures (Vol. 56, p. 104975). Elsevier.

-Lu, W. T., Phillips, B. M., & Jiang, Z. (2023). Surrogate-based cyber-physical aerodynamic shape optimization of high-rise buildings using wind tunnel testing. Journal of Wind Engineering and Industrial Aerodynamics, 242, 105586.

-Whiteman, M. L., Fernández-Cabán, P. L., Phillips, B. M., Masters, F. J., Davis, J. R., & Bridge, J. A. (2022). Cyber-physical aerodynamic shape optimization of a tall building in a wind tunnel using an active fin system. Journal of Wind Engineering and Industrial Aerodynamics, 220, 104835.

3) Figure 1: A grid expansion ratio seemed to be applied in the mesh generation. If so, the value of the expansion ratio must be reported.

4) Line 260: "..., in the context of undisturbed airflow (i.e., zero angle of attack)." How is a zero AoA considered "undisturbed airflow"? What is meant by "undisturbed"?

5) No formal equation defining the drag (or pressure) coefficient is included in the present manuscript.

6) Drag coefficient is defined as "CD". This is confusing and the "D" must be a subscript (the same with "CL").

7) Values of the reference mean wind velocity (U_H) and turbulence intensity (I_H) (Eq. 17 and 18) must be reported.

8) Line 222: Is "upper-side" = "roof"? Please use different terminology.

9) Line 286: The start of the "Results and Discussion" section sounds redundant and repeats some of the content already discussed in sections 1 and 2.

The quality of the English language is, for the most part, acceptable.

Author Response

Dear Editor,

We are very thankful to the positive and valuable comments from the editor and reviewers which expressively improve the quality of this paper. It is our great pleasure to submit the revised version of this manuscript based on the generous suggestions and comments of the reviewers, which we wish could satisfy the editor and reviewers.

Comments and Suggestions for Authors

#Reviewer 2

The manuscript applies the adjoint method to numerically perform a sensitivity analysis and assess the influence of aerodynamic shape on drag forces (CD and CL). While the approach may be effective in adjusting the aerodynamic configuration of tall buildings, the manuscript, at its present form, omits numerous details relating to the CFD simulation and some of the text requires significant improvement. Therefore, this reviewer recommends major revisions.

We firstly are grateful for the reviewer’s effort in reviewing our manuscript and the positive comments that acknowledge our paper’s contribution. The following are our replies to each question one by one:

Specific comments are included below:

1. The authors mentioned a hybrid RANS/LES CFD solver executed in ANSYS. However, many critical CFD simulation parameters (e.g., coefficients specified in the turbulence models, sub-grid turbulence modeling, etc.) still need to be reported, and only the time step was specified in the manuscript. With the current information, future researchers would be unable to replicate the results.

• Thanks for your valuable comments. The combination of LES and RANS turbulence model is called DES (Delayed Detached Simulation). The reason is that the RANS model has great examination about eddies near the wall and LES is used for larger eddies that are far from the walls. Also, the specification of the results of this turbulence model and others are compared with experimental data in Table 4.
• For sub-grid turbulence modeling this study utilizes as following:

Model: DES à  RANS Model: SST-k-omega àK-omega option: Low-Re Correlation àDES option: Delayed DES à shielding function: DDES

2. Line 54-55: The authors are missing recent wind tunnel studies directly related at aerodynamic optimization of tall buildings.

Some examples are included below:  -Li, Y., Zhu, Y., Chen, F. B., & Li, Q. S. (2023, October). Aerodynamic loads of tapered tall buildings: Insights from wind tunnel test and CFD. In Structures (Vol. 56, p. 104975). Elsevier. 

-Lu, W. T., Phillips, B. M., & Jiang, Z. (2023). Surrogate-based cyber-physical aerodynamic shape optimization of high-rise buildings using wind tunnel testing. Journal of Wind Engineering and Industrial Aerodynamics, 242, 105586. 

-Whiteman, M. L., Fernández-Cabán, P. L., Phillips, B. M., Masters, F. J., Davis, J. R., & Bridge, J. A. (2022). Cyber-physical aerodynamic shape optimization of a tall building in a wind tunnel using an active fin system. Journal of Wind Engineering and Industrial Aerodynamics, 220, 104835. 

• Thanks for your valuable comments. The updated references are added to the manuscript.

3. Figure 1: A grid expansion ratio seemed to be applied in the mesh generation. If so, the value of the expansion ratio must be reported.

• Thanks for your nice comment. The Expansion ratio of the Mesh of this study is considered 1.2.

4. Line 260: "..., in the context of undisturbed airflow (i.e., zero angle of attack)." How is a zero AoA considered "undisturbed airflow"? What is meant by "undisturbed"?

• Thanks for your kind comment. The study wants to check the mesh independency by checking the mesh results in BL1 condition. So the means of the sentence is that the wind flow without any angle of attack is disturbing towards the building and the results were compared in Table 2.

5. No formal equation defining the drag (or pressure) coefficient is included in the present manuscript.

• Thanks for your kind suggestion. The drag coefficient and pressure coefficient formula also added to the manuscript.
• Furthermore, The Lift and Drag coefficient are also calculated as follows:
•  

• Where, r is defined as radius, L, A and v are defined as Lift force, Area and velocity. Also, D is defined as Drag force in the above equations.
• The pressure coefficient is also calculated as follows:

• Where ever, p is the static pressure, is the static pressure in the freestream, is the freestream fluid density, and is the freestream velocity of the fluid.

6. Drag coefficient is defined as "CD". This is confusing and the "D" must be a subscript (the same with "CL").

• Thanks for your valuable comment. The manuscript has been revised.
•  

7. Values of the reference mean wind velocity (U_H) and turbulence intensity (I_H) (Eq. 17 and 18) must be reported.

• Thanks for your valuable comments. The value is added to the Table1.

• Table 1. Flow characteristics and turbulence intensity in the different flow conditions.

8. Line 222: Is "upper-side" = "roof"? Please use different terminology.

• Thank you for your kind comment. The manuscript revised and the authors mean to write the free stream wind velocity.

9. Line 286: The start of the "Results and Discussion" section sounds redundant and repeats some of the content already discussed in sections 1 and 2.

• Thank you for your suggestion. It removed.

Comments on the Quality of English Language

The quality of the English language is, for the most part, acceptable.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have addressed all the comments and concerns from this reviewer.