Influence of wave spreading on offshore wind turbine design: a monopile supported DTU 10-MW Turbine Case Study

Offshore ocean waves are directionally spread whereby the
propagation of energy travels in different directions. Despite this
multi-directionality, the use of 3-dimensional wave models for
loading on fixed offshore wind turbines has been limited. This
is partially due to the common assumption that uni-directional
seastates are conservative within a design philosophy. This may
not always be true given that in operating conditions the amount
of aerodynamic damping in the side-side direction is much lower
than the fore-aft direction.
This paper aims to address this issue by providing the influence of wave spreading on various offshore wind turbine design
scenarios: fatigue, ultimate and service limit state design. This
study demonstrates that wave spreading indeed results in more
fatigue damage for operating load cases. Despite this increase
in operating cases, the overall fatigue and ultimate limit state
utilization is still reduced when a wave spreading is adopted.