Table Of ContentPassive Control of Aerodynamic Load in Wind Turbine
Blades
Edgar Sousa Carrolo
Thesis to obtain the Master of Science Degree in
Aerospace Engineering
Supervisor: Professor André Calado Marta
Examination Committee
Chairperson: Professor Filipe Szolnoky Ramos Pinto Cunha
Supervisor: Professor André Calado Marta
Member of the Committee: Doctor José Lobo do Vale
June 2015
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Acknowledgments
Iwouldliketogiveawordofgratitudeinfirstplace,tomysupervisorAndre´ Martaforhistotalavailability
wheneverIneeded. Hetrustedinmesincethebeginningandgavemealltheconfidencetoovercome
thedifficultiesIhadthroughoutthiswork. Thankyouforeverything! ThegreetingisextendedtothePh
D.studentSima˜oRodriguesforhistechnicaltipsandadvices.
IwanttothankmydearfriendsandcolleaguesJose´ andDiogo,fortheirconcernaboutmyprogress
and emotional support, not only during the dissertation period but all the university time. All those who
alwayscaredaboutmearealsoincluded.
Finally, I want to thank my family, whose financial support was crucial. They never put pressure on
me,andgavemefreedomtofollowmyownpath,alwaysdemonstratingtheirconfidenceonme. Ihope,
fromnowon,throughtheworkingtoolyougavemeopportunitytoget,rewardalltheeffortyoudonein
myeducationeversince.
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Resumo
As pa´s de turbinas eo´licas com grandes dimenso˜es teˆm muitas vantagens em termos de eficieˆncia
energe´tica,noentantooseudimensionamentorepresentaummaiordesafio,devidoa`selevadascargas
aqueestasestruturasesta˜osujeitas.
Tradicionalmente, os sistemas de controlo activo permitem a` pa´ adaptar-se de acordo com as
condic¸o˜es de vento, e assim manter a sua eficieˆncia dentro de n´ıveis aceita´veis. Desde o final do
se´culo passado, alguns investigadores teˆm vindo a discutir acerca de te´cnicas de controlo passivo.
A implementac¸a˜o deste tipo de resposta aerola´stica na˜o introduz peso ou manutenc¸a˜o adicional, ao
contra´rio do controlo activo, porque na˜o existem estruturas adicionais ou complementares, e e´ muito
u´til para a reduc¸a˜o de cargas de fadiga ou optimizar a energia produzida. O objectivo passou por
conseguir uma reduc¸a˜o efectiva da carga aerodinaˆmica num modelo computacional de uma pa´. No
aˆmbito deste trabalho foram desenvolvidos modelos computacionais que simulam a interacc¸a˜o flu´ıdo-
estruturanummodelodepa´ aperfeic¸oado,efoiconsideradoinicialmentenumana´liseacoplada,apenas
acargaaerodinaˆmicaedeseguida,combinando-acomcarregamentosinerciais. Osresultadosdemon-
straramqueestedesignreduzirem2.1%acargaaerodinaˆmicanacondic¸a˜odeumventodevelocidade
ma´xima de operac¸a˜o. Uma validac¸a˜o esta´tica preliminar foi realizada com sucesso, tendo em conta
valoresma´ximosderefereˆncia.
Palavras-chave:
Adaptac¸a˜oaeroela´stica,Acoplamentoflexa˜o-torc¸a˜o,Controlopassivo,Car-
regamentoaerodinaˆmico,Interac¸a˜ofluido-estrutura.
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Abstract
Largewindturbinebladeshavemanyadvantagesintermsofpowerefficiency, despiterepresentingan
hazard concerning the high loads applied on the structure. Traditionally, there are active control sys-
tems that allow blades to adapt according to wind conditions, and so maintain power efficiency and
aerodynamic load within acceptable levels. Since the end of the last century, some researchers have
been discussing about passive control techniques. The implementation of this kind of aeroelastic re-
sponse does not bring additional maintenance or weight, unlike active control, because there are no
additionaldevicesorcomplementarystructures,andisveryusefuleithertoreducefatigueloadsorop-
timize energy output. The main purpose was to achieve an effective reduction in aerodynamic loading
inawindturbineblade. Inthescopeofthiswork,computationalmodelsweredevelopedthatsimulated
the fluid-structure interaction on a enhanced blade model. Coupled analysis considering first only the
aerodynamic load and then combining it with inertial were performed. The results demonstrated that
this design could reduce 2.1% aerodynamic load in high wind speeds at the cut-out wind speed, thus
provingtobearealisticpassivecontroltechnique. Apreliminarystaticvalidationoftheenhancedblade
modelwassuccessfullydone,takingintoaccountmaximumreferencevalues.
Keywords:
Aeroelastic Tailoring, Bend-twist Coupling, Passive Control, Aerodynamic Load,
Fluid-structureInteraction.
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Contents
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Resumo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
ListofTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
ListofFigures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 WindEnergyOverview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 HistoricPerspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2 ModernWindEnergyContext . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 ThesisOutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Horizontal-AxisWindTurbines 7
2.1 GenericOverview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 SourcesofLoadonBlades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 PowerandTorqueCharacteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 BladeDesignandProperties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.1 BladeSection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.2 BladeMaterialProperties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.3 AirfoilOptimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4.4 NumberofBlades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4.5 BladeTwistDesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4.6 BladeThickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4.7 Tip-SpeedRatio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 AerodynamicLoadControl 15
3.1 ActiveLoadControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1 VariablePitchAngleBlades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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3.1.2 ActiveFlowControlTechniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2 PassiveLoadControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.1 StallRegulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.2 AerolasticTailoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.2.3 Bend-TwistCoupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4 AerodynamicModel 22
4.1 IncompressiblePotentialFlowFundamentals . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1.1 BoundaryConditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.1.2 VortexFlow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1.3 ActuatorDiskConcept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1.4 ClassicalBladeElementMethodTheory . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2 NumericalModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.1 PanelMethod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.2 BEMIterativeSolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3 DescriptionofAerodynamicRoutineProgramaero load.m . . . . . . . . . . . . . . . . . . 32
4.3.1 PurposeandObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.2 InputVariables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.3 Pressuredistribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.3.4 BEMComputation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.4 AerodynamicLoadComputation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.4.1 ProgramRoutine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5 StructuralModel 37
5.1 LinearElasticityFoundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2 FiniteElementMatrixFormulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3 Compositematerials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.4 DescriptionofStructuralMeshGeneratorWTB struct model.m . . . . . . . . . . . . . . . 41
5.4.1 PurposesandObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.4.2 InputVariables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.4.3 NodesAssembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.4.4 ElementsAssembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.5 LoadandNodalConstraintsComputation . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
6 Fluid-StructureInteraction 45
6.1 FluidStructureInteractionMethods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
6.2 LooseCouplingFSISchemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.3 SimplifiedCouplingProcedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
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Description:Os resultados demon- this design could reduce 2.1% aerodynamic load in high wind speeds at the cut-out wind speed, thus .. List of Tables.
