Wind Turbine Blade-Tip Optimization: A Systemic Computational Approach

Round 1

Reviewer 1 Report

The paper discusses an approach for optimizing the outer and inner designs of  a curved bladelet. It lacks novelty and the followings are noted as major concerns.

- The steps of the proposed approach are not clearly explained and their mathematical descriptions are lacking.

- There are references listed at the end of the manuscript but they are not cited in the text.

- There is an incomplete paragraph in the text. Authors should read their manuscript. 

- There is no need to fabricate the part with SLA method since it is not meaningful in practice. 

Author Response

Dear reviewer,

Thank you for taking the time to review our manuscript and providing us with your feedback. We appreciate your comments and suggestions, which have helped u to improve the quality of our work. 

We have carefully considered each of your comments and would like to respond to them as follows : 

The steps of the proposed approach are not clearly explained and their mathematical descriptions are lacking.

Comment addressed: More elaborate explanations added with mathematical formulations:

• Section 2.1, line 117 to 147
• Section 2.2, line 236 to 251

- There are references listed at the end of the manuscript, but they are not cited in the text.

Comment addressed: References properly cited in the text. Missing citations due to error during export to pdf. Apologies for this inconvenience.

- There is an incomplete paragraph in the text. Authors should read their manuscript. 

Comment addressed: Manuscript retraced, could not identify incomplete paragraph, please clarify if problem persists.

- There is no need to fabricate the part with SLA method since it is not meaningful in practice.

Comment addressed: Brief explanation added:

• Section 2.3, line 315 to 318
• Section 2.3, line 327 to 329
• Section 4, lines 488-489 (relevant comment)

In short: 3D printed scaled-down bladelet will be used for further physical experimentation, not included in this current work. Translucency of the material supports visualization of the results of the topology optimization process.

We hope that our responses adequately address your concerns and have helped to clarify any issues.

You may find attached the manuscript with track-changes.

Author Response File: Author Response.docx

Reviewer 2 Report

There are quite many things need to be revised for this work:

1. Authors need to place the reference citation numbers in the manuscript. There are no references starting from the introduction until the results and discussion sections.

2. Check typing errors where there are some spaces before the periods in many sentences. Check the figure captions format. Do not add space between paragraphs.

3. Recheck again the contents, do not put unit in [ ].

4. Figures 1-2 need to redraw again to be aesthetically better and clear

5. Figure 4 needs to be redrawn for mid-optimization iterations and the final part.

6. What is Figure 13 wanted to be shown? What is the meaning of red colored part. It is not explained in body text.

7. Explained more thoroughly the result of 3D printing (properties, performance, etc.) shown in Figure 14. 

 

Author Response

Dear reviewer,

Thank you for taking the time to review our manuscript and providing us with your feedback. We appreciate your comments and suggestions, which have helped u to improve the quality of our work. 

We have carefully considered each of your comments and would like to respond to them as follows : 

1. Authors need to place the reference citation numbers in the manuscript. There are no references starting from the introduction until the results and discussion sections.

Comment addressed: References properly cited in the text. Missing citations due to error during export to pdf. Apologies for this inconvenience.

2. Check typing errors where there are some spaces before the periods in many sentences. Check the figure captions format. Do not add space between paragraphs.

Comments addressed:

• Spaces occurred due to missing citations from export error, and are now corrected.
• Captions reformatted across the manuscript (size and indents according to journal template).
• Paragraph spacing adjusted.

3. Recheck again the contents, do not put unit in [ ].

Comment addressed: Contents rechecked, square brackets removed, spaces also added between values and units overall.

4. Figures 1-2 need to redraw again to be aesthetically better and clear

Comment addressed: Figures redrawn. Text boxes simplified and fonts altered to match main text.

5. Figure 4 needs to be redrawn for mid-optimization iterations and the final part.

Comment addressed: Figure redrawn, alterations in mid-optimization iterations and final part depictions.

6. What is Figure 13 wanted to be shown? What is the meaning of red colored part. It is not explained in body text.

Comment addressed: Brief explanation added:

• Section 3.3 lines 454-454
• Figure caption extended.

In short: Red colored areas indicate areas where material should be removed for orifices need to be implemented for resin drainage after printing.

7. Explained more thoroughly the result of 3D printing (properties, performance, etc.) shown in Figure 14. 

Comment addressed: Brief description added:

• Section 2.3, line 337 to 34, text regarding relevant material properties (high strength and stiffness and translucent property).
• Section 3.2, line 415, text regarding maximum simulated stresses on bladelet against datasheet material properties.

We hope that our responses adequately address your concerns and have helped to clarify any issues.

You may find attached the manuscript with track-changes.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors presented Numerical study to optimize the Wind turbine blade-tip.

The introduction is relatively short and may be extended.

The novelty of the paper is to be clearly stated.

The used CFD method is to be detailed.

What is the used CFD software ?

The solved governing equations are to be presented.

What is the used turbulence model?

What is the considered range for Reynold number?

Have you considered time dependent or independent equations?

A figure presenting the used mesh is to be added.

A grid sensitivity test is to be performed.

A validation/verification of the numerical model is to be performed.

The optimisation method is to be formulated mathematically.

The font size of the text and legend of Fig 8 is small.

 

Author Response

Dear reviewer,

Thank you for taking the time to review our manuscript and providing us with your feedback. We appreciate your comments and suggestions, which have helped u to improve the quality of our work. 

We have carefully considered each of your comments and would like to respond to them as follows : 

1. The introduction is relatively short and may be extended.

Comment addressed: Additional text implemented:

• Section 1 (Introduction), lines 84 to 87 and line 90 mainly to state paper novelty.

2. The novelty of the paper is to be clearly stated.

Comment addressed: Additional text implemented defining the novelty of the paper.

• Abstract lines 20-21
• Section 1 (Introduction), lines 84 to 87 and line 90

3. The used CFD method is to be detailed.

Comment addressed: Additional text implemented:

• Section 2.1 line 189 to 197, regarding simulation scenario, blade configuration and domain.

 

4. What is the used CFD software?

Comment addressed: Additional text implemented:

• Section 2.1 line 205, Utilized software: Ansys Fluent R 2021

 

5. The solved governing equations are to be presented.

Comment addressed: Additional text implemented:

• Section 2.1 line 205. The governing equations of the simulations are Reynolds Averaged Navier Stokes (RANS). Corresponding literature reference also added.

 

6. What is the used turbulence model?

Comment addressed: Additional text implemented:

• Section 2.1-line 202 (Shear Stress Transfer (SST) k-ω turbulence model was utilized to capture turbulent flows).

 

7. What is the considered range for Reynold number?

Comment addressed: Additional text implemented:

• Section 2.1 line 203 (Reynolds number at the order of 2⋅106 expected, considering the geometric and operating characteristics of the wind turbine under investigation).

 

8. Have you considered time dependent or independent equations?

Comment addressed: Additional text implemented:

• Section 2.1 line 205. (Time-dependent RANS were considered).

 

9. A figure presenting the used mesh is to be added.

Comment addressed: Figure 4 added (line 200):

10. A grid sensitivity test is to be performed.

Comment addressed: Section 2.1 lines 198 and 208 to 212.

• Grid sensitivity test unavailable, although a mesh independence study was carried out during mesh refinement. Whereas the tip speed remained within 1% of the nominal design value during every mesh refinement step the difference between rated and calculated power coefficient decreased from 30.4% to 19.6% after the 4th refinement step. Further refinement of the mesh was not made possible at this point due to computational limitations.

 

11. A validation/verification of the numerical model is to be performed.

Comment addressed: Section 2.1 lines 208 to 212:

• Whereas the tip speed remained within 1% of the nominal design value during every mesh refinement step the difference between rated and calculated power coefficient decreased from 30.4% to 19.6% after the 4th refinement step. Further refinement of the mesh was not made possible at this point due to computational limitations.

Summary: Ansys Fluent R 2021 was used, with time dependent Reynolds averaged Navier Stokes (RANS) equations and a Shear Stress Transfer (SST) k-ω turbulence model. A conical shaped domain with tetrahedral elements was employed, (relevant Figure added also showing Mesh), element sizes were selected after a mesh independence study. Model verification was carried out using design values for the blade and simulation results on tip speed and power coefficient. Further refinement was prevented due to computational limitations. The simulations assumed an indicative operating scenario for the turbine to support the optimization methodology.

12. The optimization method is to be formulated mathematically.

Comment addressed: Both optimization methods (shape and topology) have been mathematically formulated, additional material added:

• Section 2.1, line 117 to 147
• Section 2.2, line 236 to 251
• Literature correspondingly updated.

13. The font size of the text and legend of Fig 8 is small.

Comment addressed: Figure edited, fonts updated both in text and legend.

We hope that our responses adequately address your concerns and have helped to clarify any issues.

You may find attached the manuscript with track-changes.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors have addressed all the issues in the revised manuscript. It can be accepted.

Reviewer 2 Report

The authors have made proper revisions to their work.

Reviewer 3 Report

Accept in present form