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Lookup NU author(s): Professor Zhiqiang Hu
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
The nonlinear coupling effect between DOFs and the influence of vortex induced loads on the motion of SPAR type FOWT are studied based on an aero-hydro-vortex-mooring coupled model. Both first- and second-order wave loads are calculated based on the 3D potential theory. The aerodynamic loads on the rotor are acquired with the blade element momentum theory. The vortex induced loads are simulated with CFD approach. The mooring forces are solved by the catenary theory and the nonlinear stiffness provided by the SPAR buoy are also considered. The coupled model is set up and a numerical code is developed for calculating the dynamic response of a Hywind SPAR-type FOWT under the combined sea states of wind, wave and current. It shows that the amplitudes of sway and roll are dominated by lift loads induced by vortex shedding, and the oscillations in roll reach the same level of pitch in some scenarios. The mean value of surge is changed under the drag loads, but the mean position in pitch, as well as the oscillations in surge and pitch, is little affected by the current. Due to the coupling effects, the heave motion is also influenced by vortex-induced forces. When vortex-shedding frequency is close to the natural frequency in roll, the motions are increased. Due to nonlinear stiffness, super-harmonic response occurs in heave, which may lead to internal resonance.
Author(s): Li Y, Liu L, Zhu Q, Guo Y, Hu Z, Tang Y
Publication type: Article
Publication status: Published
Journal: Journal of Offshore Mechanics and Arctic Engineering
Online publication date: 21/05/2018
Acceptance date: 08/04/2018
Date deposited: 15/04/2018
ISSN (print): 0892-7219
ISSN (electronic): 1528-896X
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