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Aerolastic simulation of wind turbine dynamics
KTH, School of Engineering Sciences (SCI), Mechanics.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work in this thesis deals with the development of an aeroelastic simulation tool for horizontal axis wind turbine applications.

Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. The needs for computational and experimental procedures for investigating aeroelastic stability and dynamic response have increased as wind turbines become lighter and more flexible.

A finite element model for simulation of the dynamic response of horizontal axis wind turbines has been developed. The developed model uses the commercial finite element system MSC.Marc, focused on nonlinear design and analysis, to predict the structural response. The aerodynamic model, used to transform the wind flow field to loads on the blades, is a Blade-Element/Momentum model. The aerodynamic code is developed by The Swedish Defence Research Agency (FOI, previously named FFA) and is a state-of-the-art code incorporating a number of extensions to the Blade-Element/Momentum formulation. The software SOSIS-W, developed by Teknikgruppen AB was used to generate wind time series for modelling different wind conditions.

The method is general, and different configurations of the structural model and various type of wind conditions can be simulated. The model is primarily intended for use as a research tool when influences of specific dynamic effects are investigated. Verification results are presented and discussed for an extensively tested Danwin 180 kW stall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectral properties, obtained at different conditions, have been compared with measurements. A comparison is also made between measured and calculated loads for the Tjæreborg 2 MW wind turbine during emergency braking of the rotor. The simulated results correspond well to measured data.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , xvii, 85 p.
Series
Trita-MEK, ISSN 0348-467X ; 2005:4
Keyword [en]
Applied mechanics, wind turbine, aeroelastic modelling, rotor aerodynamics, structural dynamics, MSC.Marc
Keyword [sv]
Teknisk mekanik
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-157OAI: oai:DiVA.org:kth-157DiVA: diva2:7492
Public defence
2005-04-08, Sal M3, KTH, Brinellvägen 64, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100826Available from: 2005-04-04 Created: 2005-04-04 Last updated: 2012-03-19Bibliographically approved
List of papers
1. Aeroelastic FE modelling of wind turbine dynamics
Open this publication in new window or tab >>Aeroelastic FE modelling of wind turbine dynamics
(English)In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243Article in journal (Refereed) Submitted
Abstract [en]

By designing wind turbines with very flexible components it is possible toreduce loads and consequently the associated cost. As a result, the increased flexibilitywill introduce geometrical nonlinearities. Design tools that can cope with those nonlinearitieswill therefore be necessary at some stage of the design process. The developedmodel uses the commercial finite element system MSC.Marc, which is an advanced finiteelement system focused on nonlinear design and analysis, to predict the structuralresponse. The aerodynamic model named AERFORCE, used to transform the wind toloads on the blades, is a Blade-Element/Momentum model, developed by The SwedishDefence Research Agency (FOI, previously named FFA). The paper describes the developedmodel with focus on component modelling to allow for geometrical nonlinearities.Verification results are presented and discussed for an extensively tested Danwin 180 kWstall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectralproperties, obtained at normal operational conditions, have been compared with measurements.The simulated results correspond well with measurements. Results from a bladeloss simulation are presented to exemplify the versatility of the developed code.

Keyword
wind turbine, structural dynamics, aeroelasticity, finite element, nonlinear analysis
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-5013 (URN)
Note
QC 20100826Available from: 2005-04-04 Created: 2005-04-04 Last updated: 2017-12-05Bibliographically approved
2. Emergency stop simulation using a finite element model developed for large blade deflections
Open this publication in new window or tab >>Emergency stop simulation using a finite element model developed for large blade deflections
2006 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 9, no 3, 193-210 p.Article in journal (Refereed) Published
Abstract [en]

Predicting the load in every possible situation is necessary in order to build safe and optimized structures. A highly dynamical case where large loads are developed is an emergency stop. Design simulation tools that can cope with the upcoming non-linearities will be especially important as the turbines get bigger and more flexible. The model developed here uses the advanced commercial finite element system MSC.Marc, focused on non-linear design and analysis, to predict the structural response. The aerodynamic model named AERFORCE, used to transform the wind to loads on the blades, is a blade element momentum model. A comparison is made between measured and calculated loads for the Tjaere-borg wind turbine during emergency braking of the rotor. The simulation results correspond well with measured data. The conclusion is that the aeroelastic tool is likely to perform well when simulating more flexible turbines.

Keyword
wind turbine, structural dynamics, aeroelasticity, finite element; simulation, emergency stop
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-5014 (URN)10.1002/we.154 (DOI)000238377100001 ()2-s2.0-33745121201 (Scopus ID)
Note
QC 20100826. Tidigare titel: Emergency stop simulation using a FEM model developed for large blade deflections. Uppdaterad från Accepted till Published och titel ändrad 20100826.Available from: 2005-04-04 Created: 2005-04-04 Last updated: 2017-12-05Bibliographically approved
3. Influence of wind turbine flexibility on loads and power production
Open this publication in new window or tab >>Influence of wind turbine flexibility on loads and power production
2006 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 9, no 3, 237-249 p.Article in journal (Refereed) Published
Abstract [en]

Most aeroelastic codes used today assume small blade deflections and application of loads on the undeflected structure. However, with the design of lighter and more flexible wind turbines, this assumption is not obvious. By scaling the system mass and stiffness properties equally, it is possible to compare wind turbines of different degrees of slenderness and at the same time keep system frequencies the some in an undeformed state. The developed model uses the commercial finite element system MSC. Marc, focused on non-linear design and analysis, to predict the structural response. The aerodynamic model AERFORCE, used to transform the wind to loads on the blades, is a blade element momentum model. A comparison is made between different slenderness ratios in three wind conditions below rated wind speed. The results show that large blade deflections have a major influence on power production and the resulting structural loads and must be considered in the design of very slender turbines.

Keyword
wind turbine, structural dynamics, aeroelasticity, finite element, simulation
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-5015 (URN)10.1002/we.167 (DOI)000238377100004 ()2-s2.0-33745119479 (Scopus ID)
Note
QC 20100826. Uppdaterad från Submitted till Published 20100826.Available from: 2005-04-04 Created: 2005-04-04 Last updated: 2017-12-05Bibliographically approved

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