Dynamic prescribed-wake vortex method for aerodynamic analysis of offshore floating wind turbines

A prescribed-wake vortex model for evaluating the aerodynamic loads on offshore floating turbines has been developed. As an extension to the existing UMass analysis tool, WInDS, the developed model uses prescribed empirical wake node velocity functions to model aerodynamic loading. This model is applicable to both dynamic flow conditions and dynamic rotational and translational platform motions of floating offshore turbines. With this model, motion-induced wake perturbations can be considered, and their effect on induction can be modeled, which is useful for floating offshore wind turbine design. The prescribed-wake WInDS model is shown to increase computational efficiency drastically in all presented cases and maintain comparable accuracy to the free wake model. Results of prescribed-wake model simulations are presented and compared to results obtained from the free wake model to confirm model validity.

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A Modified Free Wake Vortex Ring Method for Horizontal-Axis Wind Turbines

Energies ◽

10.3390/en12203900 ◽

2019 ◽

Vol 12 (20) ◽

pp. 3900 ◽

Cited By ~ 1

Author(s):

Jing Dong ◽

Axelle Viré ◽

Carlos Simao Ferreira ◽

Zhangrui Li ◽

Gerard van Bussel

Keyword(s):

Wind Turbine ◽

Vortex Ring ◽

Horizontal Axis ◽

Wake Vortex ◽

Horizontal Axis Wind Turbine ◽

Vortex Model ◽

Ring Method ◽

Wake Model ◽

Free Wake ◽

Platform Motions

A modified free-wake vortex ring model is proposed to compute the dynamics of a floating horizontal-axis wind turbine, which is divided into two parts. The near wake model uses a blade bound vortex model and trailed vortex model, which is developed based on vortex filament method with straight lifting lines assumption. By contrast, the far wake model is based on the vortex ring method. The proposed model is a good compromise between accuracy and computational cost, for example when compared with more complex vortex methods. The present model is used to assess the influence of floating platform motions on the performance of a horizontal-axis wind turbine rotor. The results are validated on the 5 MW NREL rotor and compared with other aerodynamic models for the same rotor subjected to different platform motions. The results show that the proposed method is reliable. In addition, the proposed method is less time consuming and has similar accuracy when comparing with more advanced vortex based methods.

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A Modified Free-Wake Vortex Ring Model for the Aerodynamics of Floating Offshore Wind Turbines

ASME 2019 2nd International Offshore Wind Technical Conference ◽

10.1115/iowtc2019-7610 ◽

2019 ◽

Author(s):

Jing Dong ◽

Axelle Viré ◽

Simao Ferreira ◽

Zhangrui Li ◽

Gerard van Bussel

Keyword(s):

Wind Turbine ◽

Vortex Ring ◽

Horizontal Axis ◽

Wake Vortex ◽

Horizontal Axis Wind Turbine ◽

Wind Speeds ◽

Vortex Model ◽

Ring Model ◽

Wake Model ◽

Free Wake

Abstract A modified free-wake vortex ring model is proposed to compute the dynamics of a floating horizontal-axis wind turbine. The model is divided into two parts. The near wake model uses a blade bound vortex model and trailed vortex model, which is developed based on vortex filament method. By contrast, the far wake model is based on the vortex ring method. This is a good compromise between accuracy and computational cost. In this work, the model is used to assess the influence of floating platform motions on the performance of a horizontal-axis wind turbine rotor. The results are validated on the 5MW NREL rotor and compared with other vortex models for the same rotor subjected to different platform motions. It was found that the result from the proposed method are more reliable than the results from BEM theory especially at small angles of attack in the region of low wind speeds, on the one hand, and high wind speeds with blade pitch motions, on the other hand.

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A Modified Free Wake Vortex Ring Method for Horizontal-Axis Wind Turbines

10.20944/preprints201908.0078.v1 ◽

2019 ◽

Author(s):

Jing Dong ◽

Axelle Viré ◽

Carlos Simao Ferreira ◽

Zhangrui Li ◽

Gerard van Bussel

Keyword(s):

Wind Turbine ◽

Vortex Ring ◽

Horizontal Axis ◽

Wake Vortex ◽

Horizontal Axis Wind Turbine ◽

Wind Speeds ◽

Vortex Model ◽

Ring Method ◽

Wake Model ◽

Free Wake

A modified free-wake vortex ring model is proposed to compute the dynamics of a floating horizontal-axis wind turbine. The model is divided into two parts. The near wake model uses a blade bound vortex model and trailed vortex model, which is developed based on vortex filament method. By contrast, the far wake model is based on the vortex ring method. The proposed model is a good compromise between accuracy and computational cost, for example when compared with more complex vortex methods. The present model is used to assess the influence of floating platform motions on the performance of a horizontal-axis wind turbine rotor. The results are validated on the 5MW NREL rotor and compared with other aerodynamic models for the same rotor subjected to different platform motions. It was found that the results from the proposed method are more reliable than the results from BEM theory especially at small angles of attack in the region of low wind speeds, on the one hand, and high wind speeds with blade pitch motions, on the other hand. And also the proposed method is less time consuming and has similar accuracy when comparing with more advanced vortex based methods.

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Dynamic Analysis of a Floating Offshore Wind Turbine Under Extreme Environmental Conditions

Volume 7: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2012-83985 ◽

2012 ◽

Cited By ~ 2

Author(s):

Tomoaki Utsunomiya ◽

Shigeo Yoshida ◽

Hiroshi Ookubo ◽

Iku Sato ◽

Shigesuke Ishida

Keyword(s):

Dynamic Analysis ◽

Wind Turbine ◽

Environmental Conditions ◽

Aerodynamic Force ◽

Experimental Results ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Simulation Code ◽

Floating Offshore Wind Turbine

This paper is concerned with the development of a Floating Offshore Wind Turbine (FOWT) utilizing spar-type floating foundation. In order to design such a structure, it is essential to evaluate the dynamic response under extreme environmental conditions. In this study, therefore, a dynamic analysis tool has been developed. The dynamic analysis tool consists of a multi-body dynamics solver (MSC.Adams), aerodynamic force evaluation library (NREL/AeroDyn), hydrodynamic force evaluation library (In-house program named SparDyn), and mooring force evaluation library (In-house program named Moorsys). In this paper, some details of the developed dynamic analysis tool are given. In order to validate the program, comparison with the experimental results, where the wind, current and wave are applied simultaneously, has been made. The comparison shows that satisfactory agreements between the simulation and the experimental results are obtained. However, when VIM (Vortex Induced Motion) occurs, the current loads and cross flow responses (sway and roll) are underestimated by the simulation since the simulation code does not account for the effect of VIM.

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Fatigue Life Analysis of Offshore Wind Turbine Support Structures in an Offshore Wind Farm

ASME 2018 1st International Offshore Wind Technical Conference ◽

10.1115/iowtc2018-1061 ◽

2018 ◽

Author(s):

Bryan Nelson ◽

Yann Quéméner

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Wind Farm ◽

The Body ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Support Structures ◽

Offshore Wind Farm ◽

Actuator Disk

This study evaluated, by time-domain simulations, the fatigue lives of several jacket support structures for 4 MW wind turbines distributed throughout an offshore wind farm off Taiwan’s west coast. An in-house RANS-based wind farm analysis tool, WiFa3D, has been developed to determine the effects of the wind turbine wake behaviour on the flow fields through wind farm clusters. To reduce computational cost, WiFa3D employs actuator disk models to simulate the body forces imposed on the flow field by the target wind turbines, where the actuator disk is defined by the swept region of the rotor in space, and a body force distribution representing the aerodynamic characteristics of the rotor is assigned within this virtual disk. Simulations were performed for a range of environmental conditions, which were then combined with preliminary site survey metocean data to produce a long-term statistical environment. The short-term environmental loads on the wind turbine rotors were calculated by an unsteady blade element momentum (BEM) model of the target 4 MW wind turbines. The fatigue assessment of the jacket support structure was then conducted by applying the Rainflow Counting scheme on the hot spot stresses variations, as read-out from Finite Element results, and by employing appropriate SN curves. The fatigue lives of several wind turbine support structures taken at various locations in the wind farm showed significant variations with the preliminary design condition that assumed a single wind turbine without wake disturbance from other units.

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Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2014.0350 ◽

2015 ◽

Vol 373 (2035) ◽

pp. 20140350 ◽

Cited By ~ 11

Author(s):

Denis Matha ◽

Frank Sandner ◽

Climent Molins ◽

Alexis Campos ◽

Po Wen Cheng

Keyword(s):

Wind Turbine ◽

Design Process ◽

Experimental Tests ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Testing Methodology ◽

Cost Of Energy ◽

Turbine Design ◽

Design And Testing

The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provided, with a focus on their ability to accommodate the coupled dynamic behaviour of floating offshore wind systems. The exemplary design and testing methodology for a monolithic concrete spar platform as performed within the European KIC AFOSP project is presented. Results from the experimental tests compared to numerical simulations are presented and analysed and show very good agreement for relevant basic dynamic platform properties. Extreme and fatigue loads and cost analysis of the AFOSP system confirm the viability of the presented design process. In summary, the exemplary application of the reduced design and testing methodology for AFOSP confirms that it represents a viable procedure during pre-design of floating offshore wind turbine platforms.

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Modeling the TetraSpar Floating Offshore Wind Turbine Foundation as a Flexible Structure in OrcaFlex and OpenFAST

Energies ◽

10.3390/en14237866 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7866

Author(s):

Jonas Bjerg Thomsen ◽

Roger Bergua ◽

Jason Jonkman ◽

Amy Robertson ◽

Nicole Mendoza ◽

...

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Entire Body ◽

Floating Offshore Wind Turbine ◽

Modeling Approaches ◽

Rigid Body Model ◽

Six Degree Of Freedom ◽

Turbine Design ◽

Floating Platforms

Floating offshore wind turbine technology has seen an increasing and continuous development in recent years. When designing the floating platforms, both experimental and numerical tools are applied, with the latter often using time-domain solvers based on hydro-load estimation from a Morison approach or a boundary element method. Commercial software packages such as OrcaFlex, or open-source software such as OpenFAST, are often used where the floater is modeled as a rigid six degree-of-freedom body with loads applied at the center of gravity. However, for final structural design, it is necessary to have information on the distribution of loads over the entire body and to know local internal loads in each component. This paper uses the TetraSpar floating offshore wind turbine design as a case study to examine new modeling approaches in OrcaFlex and OpenFAST that provide this information. The study proves the possibility of applying the approach and the extraction of internal loads, while also presenting an initial code-to-code verification between OrcaFlex and OpenFAST. As can be expected, comparing the flexible model to a rigid-body model proves how motion and loads are affected by the flexibility of the structure. OrcaFlex and OpenFAST generally agree, but there are some differences in results due to different modeling approaches. Since no experimental data are available in the study, this paper only forms a baseline for future studies but still proves and describes the possibilities of the approach and codes.

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Multibody modeling for concept-level floating offshore wind turbine design

Multibody System Dynamics ◽

10.1007/s11044-020-09729-x ◽

2020 ◽

Vol 49 (2) ◽

pp. 203-236 ◽

Cited By ~ 1

Author(s):

Frank Lemmer ◽

Wei Yu ◽

Birger Luhmann ◽

David Schlipf ◽

Po Wen Cheng

Keyword(s):

Wind Turbine ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Multibody Modeling ◽

Floating Offshore Wind Turbine ◽

Turbine Design

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A Coupled CFD/Multibody Dynamics Analysis Tool for Offshore Wind Turbines With Aeroelastic Blades

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2017-61062 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yuanchuan Liu ◽

Qing Xiao ◽

Atilla Incecik

Keyword(s):

Wind Turbine ◽

Multibody Dynamics ◽

Wind Turbines ◽

Large Scale ◽

Turbine Blades ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Analysis Tool ◽

Dynamics Analysis ◽

Offshore Wind Turbines

Aero-elasticity is an important issue for modern large scale offshore wind turbines with long slender blades. The behaviour of deformable turbine blades influences the structure stress and thus the sustainability of blades under large unsteady wind loads. In this paper, we present a fully coupled CFD/MultiBody Dynamics analysis tool to examine this problem. The fluid flow around the turbine is solved using a high-fidelity CFD method while the structural dynamics of flexible blades is predicted using an open source code MBDyn, in which the flexible blades are modelled via a series of beam elements. Firstly, a flexible cantilever beam is simulated to verify the developed tool. The NREL 5 MW offshore wind turbine is then studied with both rigid and flexible blades to analyse the aero-elastic influence on the wind turbine structural response and aerodynamic performance. Comparison is also made against the publicly available data.

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