Influence of Turbulence Intensity on the Aerodynamic Performance of Wind Turbines Based on the Fluid-Structure Coupling Method

Round 1

Reviewer 1 Report

The paper conducts bidirectionally coupled fluid-structure interaction of a NREL 5MW turbine rotor in a uniform/quiescent inflow condition and with sheared/turbulent inflow conditions with three different turbulence intensities. The analysis is conducted via unsteady RANS coupled with a layered composite model in Abaqus. The FSI results highlight the dynamic elastic deformations experienced by the turbine blades and the corresponding material stresses, in particular demonstrating the strong influence of turbulence intensity.

Overall, the paper is clearly written, interesting, and follows a sound methodological approach. The results are not especially novel or impactful, but do represent an incremental improvement both in terms of methodology for addressing wind turbine FSI and the sensitivity of blade material stresses on inflow unsteadiness. I would recommend the paper for publication, except for one relatively significant weakness, which I address below. Once this is addressed, I would reconsider my position.

The major weakness I see in the paper relates to the duration that the simulation is conducted. Section 4.1 states that the overall calculation time is 20 s. In terms of flow-through times, this is less than 2 rotor diameters, which is not enough to properly develop the wake downwind of the turbine. Although this might not have a significant affect on the blade dynamics/stresses, the authors do comment on the wake development in Fig. 14, which I argue cannot be adequately developed to a statistically steady condition. The wakes shown in Fig. 20 are similarly suspect. The inadequate duration is further evidenced by the non-stationary statistics presented in Figure 22. To address this, I would want the authors to demonstrate that the simulation duration is sufficient for the wake to be fully developed to a steady (time-averaged) condition and the displacement histories reach a statistically-steady condition.

Below are a few additional considerations, in no particular order:

1. The definition of the stress tensor in Eqn 2 is incorrect, or at least uses an inconsistent symbol for the normal stress (it is indicated with a rho symbol, rather than pressure)

2. Equation 6 for the eddy frequency (omega) uses a w symbol rather than omega, which is confusing

3. G, Y, D, and S terms in Equations 5 and 6 are defined but no expressions are provided. Either link to a reference or provide full expressions for these quantities.

4. Eqn 11 mentions boundary heat and temperature, but the problem is assumed to be incompressible and isothermal.

5. In Section 3.2, the symbol D (rotor diameter) is not defined. Suggested writing "...NREL 5MW wind turbine is D=126m..." in the first sentence.

6. Can the authors comment on the suitability of the blockage ratio that they use relative to other studies?

7. How are the CFD and FEM calculations initiatilized?

8. For simulations at different wind velocities, what is the rotational speed of the turbine? Are those cases run with a constant tip speed ratio?

9. The authors use the word "error" when they more specifically mean "difference" e.g. Table 2, Table 5, Table 6. Error denotes difference between a computed value and an established "benchmark" or "true" value, whereas I believe the authors are using it to denote the relative difference between to calculated quantities. To avoid confusion, I suggest changing the wording.

Author Response

Many thanks for giving many constructive suggestions for improving this paper, the details of the response of each question are given in the attachment, please check it and get the rely.

Author Response File: Author Response.pdf

Reviewer 2 Report

One my comment is, that the graph in Fig.1 is somehow chaotic. E.g. there is no way to end from "Fluid pressure" field, the field "The results converged" on the other hand has no input. It's not very understandable. Then some spelling errors like section 2 header etc.

Author Response

Many thanks for good advice for improving the quality of this paper, the response of this question is given in the attachment, please check it.

Author Response File: Author Response.pdf

Reviewer 3 Report

Journal- Applied science

Manuscript ID: applsci-2082512

Type of manuscript: Article

Title: Influence of turbulence intensity on the aerodynamic performance of wind turbines based on the fluid-structure coupling method

The study presents an investigation to ensure the safety of wind turbine blades and to study of air-elastic response of wind turbine blades under turbulent wind. Some commercial codes are used for CFD numerical and structural simulations. In general de paper is nice and easy to read, however I do not see (or it is not well explained) the novelty and innovation of this work in comparison with other similar studies.

The scientific content is nice and suitable for a high quality journal such as Applied Science. However, some issues have to be addressed.

 

The abstract is well written and organized; enough to understand the core of the paper.

INTRODUCTION: The introduction is well written and structured. However, a deep review of the state of the art is not acutely described and explained. Solely 12 references are introduced to explain the state of the art. The current reviewer miss a lot some studies about basic cases, such as DOI10.3390/en10060742 or DOI10.3390/su11102809

 

3.2. CFD Validation- Are the CFD simulation validated versus real experiments? My main concern is based on the mesh around the Blade. The authors state that they used the well known K-omega SST for turbulence modelling. That model requires a wall yPlus less than 1 in all the walls studied. Please could you show the wall y+ into the blades? How is the wall y+ in the tip of the blade? Can you shoe more detail about the mesh in the root and in the tip of the blade? Can you showin a table the mesh quality parameters?

 

Section of results and discussion is well addressed.

 

Section 5: Conclusion. The conclusions are well numbered and described in an exhaustive way. They are also well supported by the results.

In general, please, make the figures more clear and with higher resolution.

Finally, the English writing style and grammar have to be thoroughly checked. IT IS MANDATORY!!!

 

Author Response

Many thanks for giving many constructive suggestions for improving this paper, the details of the response of each question are given in the attachment, please check it and get the rely.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have adequately addressed my concerns, to the point where I recommend publishing. Note that I believe an omega symbol is missing on line 137, or perhaps it is not rendering properly on my computer.

Reviewer 3 Report

All my comments and suggestions have been successfully addressed. Final English grammar and style corrections are recommended