A simulation study demonstrating the importance of large-scale trailing vortices in wake steering

Fleming, Paul; Annoni, Jennifer; Churchfield, Matthew; Martinez-Tossas, Luis A.; Gruchalla, Kenny; Lawson, Michael; Moriarty, Patrick

doi:https://doi.org/10.5194/wes-3-243-2018

Articles | Volume 3, issue 1

https://doi.org/10.5194/wes-3-243-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/wes-3-243-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 3, issue 1

Research article

|

14 May 2018

Research article |

| 14 May 2018

A simulation study demonstrating the importance of large-scale trailing vortices in wake steering

Paul Fleming, Jennifer Annoni, Matthew Churchfield, Luis A. Martinez-Tossas, Kenny Gruchalla, Michael Lawson, and Patrick Moriarty

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Final revised paper (published on 14 May 2018)
Preprint (discussion started on 22 Nov 2017)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Interactive comment on »From wake steering to flow control«', Anonymous Referee #1, 11 Jan 2018
- AC1: 'Response to reviewer 1', Paul Fleming, 25 Jan 2018
RC2: 'Interesting findings for wind farm control', Anonymous Referee #2, 23 Jan 2018
- AC2: 'Response to reviewer 2', Paul Fleming, 25 Jan 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Paul Fleming on behalf of the Authors (25 Jan 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Feb 2018) by Carlo L. Bottasso

RR by Anonymous Referee #2 (23 Feb 2018)

RR by Anonymous Referee #1 (03 Apr 2018)

Suggestions for revision or reasons for rejection

The thoroughly revised paper “A simulation study demonstrating the importance of large-scale trailing vortices in wake steering” by Fleming et al. is well structured and almost addressed all comments of the previous review.
The main changes in the title, abstract and conclusions fit now to the delivering content of the paper. The major aspects are addressed for further publication in the Wind Energy Science journal. However, the following technical and minor comments should be considered.

Scientific comments:

1. P01. L18: The first two sentences read like wake deflection always (for all conditions, layouts, ...) leads to a large power gain. We did not address this in the first review but please rephrase the sentence and explicitly state that the net increase is referring to overall wind farm energy yield.

2. Previous Comment 38 on Fig. 3: We would prefer a different color scheme which conserves the content in grayscale as well as in color. Being consistent in the publications may be a desirable goal. However, from our point of view, it should be more important that the results are presented in the best possible way. Furthermore, we have to assume that if this issue is not addressed in this publication it is not going to be addressed in future work as well for the sake of consistency. The reviewer is convinced that a color scale can be found which meets the condition and can represent the desired velocity range.

Editorial comments:

1. Sometimes the authors use “Fig.” and sometimes “Figure”. Please be consistent.

2. P04. For Figure 1 and Figure 3 the authors state if the flow is shown from above or below and upstream or downstream. We assume it does not change for Figures 5,6, 7 and 13. Nevertheless, it should be stated once for all graphs or individually in all captions.

3. P04. L08: “;” between multiple consecutive citations instead of “,.” (consistency throughout the paper)

4. P04. L07: year missing for reference: Katić

5. P04. L28: typo “.” inside bracket: “… (see Fig 1.) Fig1 ...”

6. P05. Fig.1: See previous #33. A coordinate system is still missing. It can be added as X and Y, i.e., streamwise and lateral horizontally direction, respectively. See also previous #26. Figure 1: Without a grid or ticks the use of the tick labels is limited.

7. P05. L04: The referencing of FAST should be modified. Year is missing. In general the citation through the paper needs revision.

8. P05. L14: “The simulation had 6% turbulence intensity with a shear exponent of 0.085.” 6% TI at hub height?

9. P05. L16: “The simulations include National Renewable Energy Laboratory’s (NREL’s) 5-MW reference turbines from Jonkman et al. (2009), modeled as an actuator disk for computational efficiency.” => Please add “actuator disc with rotation” as you said you did in your response to previous comment #18. The following sentence suggests its use but it does not hurt to explicitly state it.

10. P10. L13: “25°yaw” - The template seems to account for only a very very small space between a degree sign and the next word/character. This looks unusual.

11. P10. L14: "." missing at end of sentence after “Fig. 5”

12. P13 Fig. 8 (see previous comment #54): add “at hub height” in the caption

13. P14: It is better to merge section 5 with section 4, which represents the same two-turbine case study.

14. P14: Please correct the following typos, e.g., L13: ie, L16: ¼ D, L18: 2 D, L20: 14 D

15. P14. L02: typo? “In the previous section, the concept of “secondary steering” is introduced, wherein, a steered wake, causes a deflection of the wake of a downstream turbine, this is not yawed. “ => “…, which is not yawed.”?

16. P14. L09: Please rephrase this sentences "However, a possible alternative …" → the explanation is that the upstream turbine is producing a partial wake scenario vs the "secondary steering" could be related to the partial wake condition

17. P14. L15: The sentence “The front turbine is moved down ...” is complex including too much information.

18. P14. L21: Grammar revision is needed for sentence “you can that ...”.

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ED: Publish subject to technical corrections (11 Apr 2018) by Carlo L. Bottasso

ED: Publish subject to technical corrections (11 Apr 2018) by Joachim Peinke (Chief editor)

AR by Paul Fleming on behalf of the Authors (28 Apr 2018) Author's response Manuscript

Short summary

This paper investigates the role of flow structures in wind farm control through yaw misalignment. A pair of counter-rotating vortices is shown to be important in deforming the shape of the wake. Further, we demonstrate that the vortex structures created in wake steering can enable a greater change power generation than currently modeled in control-oriented models. We propose that wind farm controllers can be made more effective if designed to take advantage of these effects.