Dynamic Analysis of an Offshore Wind Turbine Including Soil Effects

Abhinav, K. A.; Saha, Nilanjan

doi:10.1016/j.proeng.2015.08.261

Cited by 28 publications

(17 citation statements)

References 11 publications

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“…The full aero-hydro-servo-elastic behavior of the structure was represented by two decoupled models. It has been noted [4] that this decoupled analysis method can adequately simulate the structure's response if the forcing frequencies of the loads do not approach the structure's natural frequency. The interface between the two models is the yaw bearing that connects the wind turbine to the tower.…”

Section: Modelmentioning

confidence: 99%

The Influence of Flexible Towers on the Dynamics of Offshore Wind Turbine Gravity Base Structures

O'Leary

Pakrashi

Kelliher

2018

Lecture Notes in Civil Engineering

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With offshore wind turbines increasing in size, there is increasing interest in non-traditional support structures. New concepts include lightweight and flexible fiberglass composite towers that have potential benefits over traditional stiff steel towers. The aim of this paper was to assess how the combination of a more flexible wind turbine tower with an offshore concrete gravity base foundation would affect the dynamic response of the structure. The results focus on how the dynamic amplification factors (DAFs) change with varying levels of foundation stiffness during an extreme event (50 year return period extreme event).

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Section: Modelmentioning

confidence: 99%

The Influence of Flexible Towers on the Dynamics of Offshore Wind Turbine Gravity Base Structures

O'Leary

Pakrashi

Kelliher

2018

Lecture Notes in Civil Engineering

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“…This increase in the structure's flexibility, following the decrease in the soil stiffness, changes the structure's responses under a certain loading case. Abhinav and Saha reported that the displacement of the wind turbine in soft clay exceeded the serviceability limit of 0.2 m at mudline. Harte et al investigated the along‐wind forced vibration response of an onshore wind turbine.…”

Section: Effects Of Base Dynamics On Foundation Loadsmentioning

confidence: 99%

“…The literature shows that the reduction in the natural frequency is usually associated with higher displacement response, for example, Abhinav and Saha showed that for a 5 MW NREL wind turbine installed in 20 m water depth with a monopole foundation system, the natural frequency was 0.24 Hz for stiff clay soil, and was reduced by 12.5% and 33.3% when the soil type was changed to medium stiff clay and soft clay, respectively. This increase in the structure's flexibility, following the decrease in the soil stiffness, changes the structure's responses under a certain loading case.…”

Section: Effects Of Base Dynamics On Foundation Loadsmentioning

confidence: 99%

On the evaluation of wind loads for wind turbines' foundation design: Experimental and numerical investigations

Abdelkader

Aly

Rezaee

et al. 2017

Struct Design Tall Spec Build

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Summary In the past two decades, wind farms have been enjoying renewed interest as means for clean and renewable energy production. Larger and taller wind turbines are used for harvesting wind energy. In this paper, a boundary‐layer wind tunnel experiment was carried out on a model of the 5‐MW National Renewable Energy Laboratory (NREL) wind turbine, to evaluate overall wind‐induced base loadings in a parked condition. While mean and background base loadings were measured experimentally, a posttest dynamic analysis framework is developed to assess inertial loads analytically. The analytical analysis is carried out under both rigid and flexible tower‐foundation assumptions. Whenever applicable, the wind tunnel measurements are compared with NREL results, which were obtained by using the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) software. The comparison shows a good agreement between the proposed approach and the available FAST results. In addition, the study indicates that the flexibility of the foundation may result in a reduced overall wind loads, due to base isolation effects. However, the assumption of a rigid foundation results in a slightly conservative base loads. This said, depending on the available foundation system, the methodology followed in the current paper remains in force and the base stiffness can be updated to permit the estimation of actual foundation loadings.

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“…These simulations are, therefore, often carried out with different analysis methods, such as frequency-domain calculations (van der Tempel and de Vries, 2005;Ziegler et al, 2015), substructuring techniques (van der Valk and Rixen, 2012), and/or simplified or reduced models . For most of the reduced models the aerodynamic loading is simplified by removing the rotor nacelle assembly from the support structure and replacing the aeroelastic computation with precomputed or stochastic generated rotor loads acting as a point force or moment at tower top (Dong et al, 2011;Abhinav and Saha, 2015;Kim and Lee, 2015;van der Male and Lourens, 2015;Schløer, et al, 2016;Ong et al, 2017) The main advantages are the faster simulation time, since the aeroelastic computation rather is a time-consuming task, and the possibility to use standard finite-element or multi-body software . It has been shown that the use of rotor load time series combined with an efficient substructuring technique (van der Valk and Rixen, 2012) can speed up the dynamic analysis for a commercial support structure design by a factor of 375.…”

Section: Introductionmentioning

confidence: 99%

Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping

Schafhirt

Muskulus

2018

Wind Energ. Sci.

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Abstract. Decoupled load simulations are a computationally efficient method to perform a dynamic analysis of an offshore wind turbine. Modelling the dynamic interactions between rotor and support structure, especially the damping caused by the rotating rotor, is of importance, since it influences the structural response significantly and has a major impact on estimating fatigue lifetime. Linear damping is usually used for this purpose, but experimentally and analytically derived formulas to calculate an aerodynamic damping ratio often show discrepancies to measurement and simulation data. In this study decoupled simulation methods with reduced and full rotor loads are compared to an integrated simulation. The accuracy of decoupled methods is evaluated and an optimization is performed to obtain aerodynamic damping ratios for different wind speeds that provide the best results with respect to variance and equivalent fatigue loads at distinct output locations. Results show that aerodynamic damping is not linear, but it is possible to match desired output using decoupled models. Moreover, damping ratios obtained from the empirical study suggest that aerodynamic damping increases for higher wind speeds.

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Dynamic Analysis of an Offshore Wind Turbine Including Soil Effects

Cited by 28 publications

References 11 publications

The Influence of Flexible Towers on the Dynamics of Offshore Wind Turbine Gravity Base Structures

The Influence of Flexible Towers on the Dynamics of Offshore Wind Turbine Gravity Base Structures

On the evaluation of wind loads for wind turbines' foundation design: Experimental and numerical investigations

Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping

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