Analysis of wake dynamics in floating offshore wind turbines under platform surge motion

Floating Offshore Wind Turbines (FOWTs) represent a promising technology for exploiting the wind resources available in deep-water regions. However, the dynamic response of the floating platform introduces additional complexity to the aerodynamic behaviour of wind turbine wakes. This thesis investigates the wake aerodynamics of an offshore wind turbine under prescribed platform surge motions. Large Eddy Simulations (LES) are performed to reproduce the turbulent flow around the wind turbine. The Actuator Line Method (ALM) is coupled with LES to represent the aerodynamic forces exerted by the blades on the flow, allowing different turbine configurations with prescribed motion conditions to be investigated and compared. The aim is to assess the influence of platform motion dynamics on the downstream flow field and wake dynamics. To analyse the large amount of data generated by the CFD simulations, a dedicated post-processing framework is developed. OpenFOAM simulation data are processed to perform a Hilbert Proper Orthogonal Decomposition (HPOD), providing spatial modes and their associated energy content. The resulting modes can be reconstructed in a format compatible with standard OpenFOAM files, enabling their direct visualisation in ParaView. The POD methodology is first validated on a canonical cylinder wake and the results are compared with established results from the literature. The validated framework is subsequently applied to the wind turbine simulations, with particular attention given to the identification of the dominant coherent structures and their evolution. The results of this study can contribute to a better understanding of the relationship between floating platform motion and wake dynamics.