Model tests were conducted on three generic floating wind turbine systems in 2011 and reported in a series of papers at the 31st Ocean, Offshore, and Arctic Engineering Conference in 2012. These tests were conducted at the MARIN facility in The Netherlands, by a consortium of universities, government research organizations, and industry. As part of the testing program, decay tests in platform pitch were conducted with and without wind forcing. It was found that for spar and semisubmersible type structures, resonant pitch motion was damped due to wind in storm sea conditions. The nonlinear decay motion of a floating wind turbine platform is modeled using a one degree-of-freedom nonlinear oscillation equation about a mean offset angle. Attention is paid to the turbine thrust coefficient and its variability with respect to oncoming flow speed, which in turn is affected by the structure pitch motion. The equation of motion reveals that the mean offset position has an important role in the stiffness, damping, and consequently the natural period of pitch motion. Several important dimensionless parameters are introduced. The paper discusses a simple thrust model for an offshore wind turbine (OWT) based on rudiments of blade element theory. Using the simplified thrust coefficient formulation, the increase in platform pitch damping due to wind is formulated. Experimental data reported from prior tests described above show good agreement with the theoretical model.
[1]
A. Goupee,et al.
Methodology for Wind/Wave Basin Testing of Floating Offshore Wind Turbines
,
2012
.
[2]
Rupp Carriveau,et al.
Fundamental and Advanced Topics in Wind Power
,
2011
.
[3]
Stefano Mauro,et al.
Wind turbine CFD modeling using a correlation-based transitional model
,
2013
.
[4]
Subrata Kumar Chakrabarti,et al.
Offshore Structure Modeling
,
1994
.
[5]
Dominique Roddier,et al.
WindFloat: A floating foundation for offshore wind turbines
,
2010
.
[6]
Bonjun Koo,et al.
Model Tests for a Floating Windturbine on Three Different Floaters
,
2012
.
[7]
Hiroyuki Fujioka,et al.
An Approach for the Optimum Design of TLP Type Offshore Wind Turbines
,
2011
.
[8]
Bonjun Koo,et al.
Experimental Comparison of Three Floating Wind Turbine Concepts
,
2012
.
[9]
Sandy Butterfield,et al.
Feasibility of Floating Platform Systems for Wind Turbines: Preprint
,
2004
.