scholarly journals The effect of breaking wave induced currents on an offshore wind turbine foundation

2011 ◽  
Author(s):  
S.-J. Choi ◽  
O. T. Gudmestad
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Induced Currents ◽  
Wave Induced

Actuator Saturation Control of Floating Wind Turbines

2012 ◽  
Author(s):  
Roberto Ramos
Keyword(s):  
Wind Turbine ◽  
Actuator Saturation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Rigid Body Model ◽  
Integral Controller ◽  
Proportional Integral Controller ◽  
Saturation Effects ◽  
Wave Induced ◽  
Blade Element

A state feedback aerodynamic controller is proposed for the stabilization and reduction of platform/tower pitch vibrations of a spar-type floating wind turbine, considering blade pitch saturation effects. The controller is synthesized from a linearized rigid body model developed for a NREL 5-MW offshore wind turbine operating at the above rated condition (region 3). Wind turbulence and wave induced loads are obtained from the blade element momentum (BEM) aerodynamic theory and Morison’s equation, respectively. The simulation results show that the proposed nonlinear control system yields significant vibration reduction in comparison to a proportional-integral controller.

The Dynamic Response of an Offshore Wind Turbine With Realistic Flexibility to Breaking Wave Impact

2011 ◽  
Author(s):  
Erik Jan de Ridder ◽  
Pieter Aalberts ◽  
Joris van den Berg ◽  
Bas Buchner ◽  
Johan Peeringa
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Breaking Waves ◽  
Impulsive Loading ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Extreme Waves ◽  
Wave Impact ◽  
Pilot Model

The effects of operational loads and wind loads on offshore monopile wind turbines are well understood. For most sites, however, the water depth is such that breaking or near-breaking waves will occur causing impulsive excitation of the monopile and consequently considerable stresses and displacements in the monopile, tower and turbine. To investigate this, pilot model tests were conducted with a special model of an offshore wind turbine with realistic flexibility tested in (extreme) waves. This flexibility was considered to be necessary for two reasons: the impulsive loading of extreme waves is very complex and there can be an interaction between this excitation and the dynamic response of the foundation and tower. The tests confirmed the importance of the topic of breaking waves: horizontal accelerations of more than 0.5g were recorded at nacelle level in extreme cases.

Cyclic Soil Loads on an Offshore Wind Turbine During Storm

2018 ◽  
Author(s):  
Shaofeng Wang ◽  
Torben J. Larsen
Keyword(s):  
Wind Turbine ◽  
Wave Theory ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Cyclic Loads ◽  
Linear Wave ◽  
Pile Settlement ◽  
Cyclic Degradation

Offshore wind turbines are subjected to combined static and cyclic loads due to its self weight, wind, current and waves. For the design of support structures, a point of concern is whether the highly varying loads may cause cyclic degradation of the soil leading to a permanent undesired pile settlement and tilting for the wind turbine. In particular during a severe storm, the large cyclic loads are being more critical as the wind and waves are typically from a single direction. The DTU 10MW wind turbine supported by a jacket at 33 m water depth is considered in this study, where the piles are axially loaded in order to bear the moment under wind and wave actions. This paper investigates the cyclic loads using traditional linear irregular waves and fully nonlinear irregular waves realized from the wave solver Ocean-Wave3D previously validated until near-breaking wave conditions. This study shows that the nonlinear irregular waves introduce more extreme cyclic loads, which result in significantly larger pile settlement than using linear wave realizations. For the case in this study, linear wave theory underestimates pile settlement at least 30% compared to nonlinear wave realizations.

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