19 Feb 2024
 | 19 Feb 2024
Status: this preprint is currently under review for the journal WES.

Investigation of blade flexibility effects over the loads and wake of a 15 MW wind turbine using a flexible actuator line method

Francois Trigaux, Philippe Chatelain, and Grégoire Winckelmans

Abstract. This paper investigates the impact of the blades flexibility on the aerodynamics and wake of large offshore turbines using a flexible actuator line method (ALM) coupled to the structural solver BeamDyn in Large Eddy Simulations. The study considers the IEA 15-MW reference wind turbine in close-to-rated operating conditions. The flexible ALM is first compared to OpenFAST simulations and is shown to consistently predict the rotor aerodynamics and the blades structural dynamics. However, the effect of the blade flexibility on the loads is more pronounced when predicted using the ALM than using the blade element momentum theory. The wind turbine is then simulated in a neutral turbulent atmospheric boundary layer with flexible and rigid blades. The significant flapwise and torsional mean displacements lead to an overall decrease of 14 % in thrust and 10 % in power compared to a rotor with no deformation. These changes influence the wake through reduced time-averaged velocity deficit and turbulent kinetic energy. The unsteady loads induced by the rotation in the sheared wind and the turbulent velocity fluctuations are also substantially affected by the flexibility and exhibit a noticeably different spectrum. However, the influence of these load variations is limited over the wake, and the assumption of rigid blades in their deformed geometry is shown to be sufficient to capture the wake dynamics. The influence of the resolution of the flow solver is also evaluated, and the results are shown to remain consistent between different spatial resolutions. Overall, the structural deformations have a substantial impact on the turbine performance, loads and wake, which emphasizes the importance of considering the flexibility of the blades in simulations of large offshore wind turbines.

Francois Trigaux, Philippe Chatelain, and Grégoire Winckelmans

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2024-19', Anonymous Referee #1, 05 Mar 2024
  • RC2: 'Comment on wes-2024-19', Anonymous Referee #2, 11 Mar 2024
Francois Trigaux, Philippe Chatelain, and Grégoire Winckelmans
Francois Trigaux, Philippe Chatelain, and Grégoire Winckelmans


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Short summary
In this research, we use numerical simulations to investigate the impact of the blades flexibility on a very large wind turbine. We show that it decreases the power production and affects the aerodynamic loads. The wind flow behind the turbine is also modified, and presents a higher mean velocity than predicted without considering the blades flexibility. Our study highlights that including the flexibility effect in the simulation of large wind turbines is important to obtain accurate results.