Articles | Volume 10, issue 10
https://doi.org/10.5194/wes-10-2137-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.On the wake re-energization of the X-Rotor vertical-axis wind turbine via the vortex-generator strategy
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- Final revised paper (published on 07 Oct 2025)
- Preprint (discussion started on 28 Jan 2025)
Interactive discussion
Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
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- RC1: 'Comment on wes-2025-3', Anonymous Referee #1, 14 Apr 2025
- RC2: 'Comment on wes-2025-3', Anonymous Referee #2, 15 May 2025
- AC1: 'Reviewer Reponses for Wes-2025-3', David Bensason, 02 Jun 2025
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by David Bensason on behalf of the Authors (02 Jun 2025)
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Author's tracked changes
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ED: Referee Nomination & Report Request started (06 Jun 2025) by Oguz Uzol
RR by Anonymous Referee #2 (03 Jul 2025)
RR by Anonymous Referee #1 (03 Jul 2025)
ED: Publish as is (03 Jul 2025) by Oguz Uzol
ED: Publish as is (07 Jul 2025) by Sandrine Aubrun (Chief editor)
AR by David Bensason on behalf of the Authors (27 Jul 2025)
This paper presents an experimental investigation regarding vortex generator (i.e. blade pitch based) wake recovery strategies for an X-Rotor type Vertical Axis Wind Turbine (VAWT). Stereoscopic PIV measurements are conducted in an open jet wind tunnel up to 6D downstream of the X-rotor on cross-stream planes within the wake. Data are obtained for three different blade pitch configurations (for the upper blades of the X rotor only) and the impact on wake characteristics, wake recovery and wake vortex dynamics are discussed. The paper is well written in general. Few points that might be considered for improving the paper are listed below:
1) Please provide a trade-off analysis quantifying the power loss from the upstream turbine when it's operated at different pitched cases versus the potential energy gains obtained within the wake.
2) In addition to thrust coefficients, please provide a table showing the power coefficient levels at different pitch angles as well.
3) Please discuss scaling issues. This turbine operates at a very low Reynolds number when compared to its full scale counterpart. How would this affect the wake vortex dynamics, which is discussed in detail for the scaled turbine.
4) How would this control strategy be implemented on a real full size turbine? What would the authors recommend regarding the necessity of dynamic pitch actuation since a static pitch control would be impractical? Would a dynamic pitch actuation result in similar wake vortex dynamics and recovery?
5) Also please comment on the expected effects of freestream turbulence and wind shear on the observed vortex dynamics within the wake. Current experiments are performed at a very low freestream turbulence level and uniform inflow conditions, which is not realistic in actual wind farms.
6) Adding some wake turbulence related information would be nice. I understand the authors have used only 300 vector maps for averaging, which is not enough to obtain converged statistics, but it would still provide a good supporting information for the arguments presented in the paper, since turbulence has a major effect in wake recovery and the wake dynamics.
7) Please place the coordinate axes exactly at the origin in Figure 4 to clearly show where the origin is. Also, y-axis is defined as a lateral coordinate and z-axis is referred to as an "axial" coordinate. In reality z-axis is not an axial coordinate. The x-axis, which shows the main streamwise direction, is an axial coordinate so I would recommend not referring to z-axis as an axial coordinate.
8) Regarding presentation of results, the beta=0 baseline case is always presented as a middle figure but in the text it's always discussed first since that is the baseline reference case. I understand the current layouts showing beta=-10 deg first followed by beta=0 deg and beta=10 deg, but this layout makes it difficult for the reader to follow the figures when reading the text.
9) Freestream wind speed of 2.7 m/s is quite low, and therefore difficult to measure with low uncertainty. What is the estimated uncertainty level for this parameter?