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Large Eddy Simulations of floating wind turbine flows for the development of floating wind farm engineering tools

MEGEP (Mécanique, Energétique, Génie civil & Procédés) – [Subject to defense authorization]

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The recent emergence of floating wind turbines, along with the prospect for their large-scale deployment in deep-sea wind farms, introduces new challenges in modeling and understanding the associated flow dynamics. Unlike fixedbottom turbines, floating ones are subject to wave-induced motions that affect both their individual performance and their interactions within wind farms.
While the past two decades have seen significant advances in understanding the dynamics of floating platforms and the aerodynamics of isolated rotors — largely driven by multi-fidelity numerical simulations — wake behavior in the presence of turbine motion remains relatively underexplored, particularly in the context of wind farms.
This thesis addresses these questions using high-fidelity numerical simulations, specifically large-eddy simulations (LES) that resolve the full geometry of the turbine. A wall-modeled LES approach is employed to capture nearwall effects, in contrast to more common actuation-based methods such as actuator disks or actuator lines. A dedicated framework was developed to simulate periodic axial motion of the turbine and to allow for rotational speed control. The methodology was validated against wind tunnel experiments on static, scaled turbines, and was used to characterize the formation of coherent structures in the wake induced by turbine motion, as well as their influence on wake mixing with the surrounding flow.

A complementary study was conducted at the farm scale using a static actuator disk model, which is more computationally efficient for large-scale simulations. While more simplified, this model was used to assess the accuracy of low-order wake models.

Jury

Laurent Bricteux	Université de Mons	Reviewer
Stéphane Aubert	Ecole Centrale de Lyon (LMFA)	Reviewer
Guillaume Balarac	Grenoble INP – UGA (LEGI)	Examiner
Laurent Gicquel	Cerfacs	Thesis supervisor
Nicolas Odier	Cerfacs	Thesis co-supervisor