A comparison of the influence of using empirical or mathematically pre-defined wave energy spectra for tower base bending fatigue calculations
Vlachogiannis, P; Peyrard, C; Pillai, AC; et al.Collu, M; Ingram, D
Date: 26 January 2024
Conference paper
Publisher
American Society of Mechanical Engineers (ASME)
Publisher DOI
Abstract
In the structural design of Floating Offshore Wind Turbines
(FOWT), fatigue plays a critical role in determining the final
design of the system. The fatigue loads are the result of combined
aerodynamic and hydrodynamic forces acting on the elastic
structure. The industry standard approach for assessing the
fatigue loads ...
In the structural design of Floating Offshore Wind Turbines
(FOWT), fatigue plays a critical role in determining the final
design of the system. The fatigue loads are the result of combined
aerodynamic and hydrodynamic forces acting on the elastic
structure. The industry standard approach for assessing the
fatigue loads involves grouping the environmental conditions
into bins. These conditions include wind speed and direction,
wave height, period and direction and the sea state spectral
shape. In shallow seas with limited fetch the JONSWAP
spectrum, or a JONSWAP-derived spectrum, is normally fitted
to the site conditions and used, which also includes a peak
enhancement factor (GAMMA) in a range defined by the
significant wave height and peak period. However, this
adjustment is sensitive to the parameter fitting process, while the
vital Peak Enhancement Factor (gamma) parameter is
commonly chosen as an arbitrary empirical value in the given
range.
In this paper, we examine how the calculation of bending fatigue
of the tower base of the IEA 15MW open source turbine
supported by the UMaine VolturnUS semi-submersible is
influenced by either the use of empirical spectra (measured or
simulated for the specific site) against pre-described site-fitted
formulas for spectral shape, and the use of different spectra per
hourly sea state against a single spectrum per data bin.
The results indicate an influence of both the used spectral shape
as well as the use of spectra for each sea state instead of a single
spectrum per bin of data.
Engineering
Faculty of Environment, Science and Economy
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