| dc.description.abstract | This thesis explores the aerodynamic performance of floating offshore wind
turbines (FOWTs) using a potential flow approach. The primary objective is
to understand how the output power of an FOWT is affected by imposing
different motions on the substructure. To this end, I employ an aerodynamic
model based on the well-known unsteady vortex-lattice method (UVLM) to
simulate the aerodynamic behaviour of the turbines in combination with a
UVLM-oriented mesh generator (UVLMeshGen, developed at the University
of Bergen) to build the aerodynamic grids. As part of this thesis, I have also
integrated into UVLMeshGen the capacity of: meshing spar-like substructures,
generating boundary surfaces intended for representing sea waves, and the
kinematics associated with both the substructure’s motion and sea waves.
Initially, the aerodynamic model of fixed and floating offshore wind turbines were validated against well-established benchmarks, including the NREL
5 MW, DTU 10 MW RWT, and Sandia 13.2 MW turbines. Following this,
various motion scenarios were simulated to investigate the effects of individual
and combined heave, surge, and wind turbine pitch motions on the power output. The results showed that the surge motion has the most significant impact
on the power, while the heave motion has the least. However, the heave motion
greatly affects the shape of the wake.
In addition, I analyze the effect of including sea waves, as a boundary
surface with imposed kinematics, on the output power of stand-still FOWTs.
The findings indicate that higher wave amplitudes produces a slight increase
in power output, the so-called blocking effect in aeronautics. Such findings
undoubtedly require further investigations in this direction to fully understand
and characterize such a phenomenon.
Finally, simulations of multiple FOWTs demonstrated the importance of
considering wake interactions when designing wind farm layouts. FOWTs
placed in close proximity showed reduced power output due to wake interference, highlighting the need for accounting wake interactions when optimizing
wind farm layouts and operating wind farms.
This research contributes to the field of renewable energy by enhancing
the predictive capabilities of aerodynamic simulations for FOWTs. It provides
a framework for future studies to incorporate more complex wave-structure
interactions and optimise the design and placement of floating wind turbines
to maximise the power production. | |
