Medium fidelity modelling of loads in wind farms under non-neutral ABL stability conditions – a full-scale validation study: Paper

Gunner Chr. Larsen, Torben J. Larsen, A. Chougule

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    The aim of the present paper is to demonstrate the capability of medium fidelity modelling of wind turbine component fatigue loading, when the wind turbines are subjected to wake affected non-stationary flow fields under non-neutral atmospheric stability conditions. To accomplish this we combine the classical Dynamic Wake Meandering model with a fundamental conjecture stating: Atmospheric boundary layer stability affects primary wake meandering dynamics driven by large turbulent scales, whereas wake expansion in the meandering frame of reference is hardly affected. Inclusion of stability (i.e. buoyancy) in description of both large- and small scale atmospheric boundary layer turbulence is facilitated by a generalization of the classical Mann spectral tensor, which consistently includes buoyancy effects. With non-stationary wind turbine inflow fields modelled as described above, fatigue loads are obtained using the state-of-the art aeroelastic model HAWC2. The Lillgrund offshore wind farm (WF) constitute an interesting case study for wind farm model validation, because the WT interspacing is small, which in turn means that wake effects are significant. A huge data set, comprising 5 years of blade and tower load recordings, is available for model validation. For a multitude of wake situations this data set displays a considerable scatter, which to a large degree seems to be caused by atmospheric boundary layer stability effects. Notable is also that rotating wind turbine components predominantly experience high fatigue loading for stable stratification with significant shear, whereas high fatigue loading of non-rotating wind turbine components are associated with unstable atmospheric boundary layer stratification.
    Original languageEnglish
    Title of host publicationWake Conference 2017
    Number of pages10
    Publication date2017
    Article number012026
    Publication statusPublished - 2017
    EventWake Conference 2017 - Visby, Sweden
    Duration: 30 May 20171 Jun 2017


    ConferenceWake Conference 2017
    Internet address
    SeriesJournal of Physics: Conference Series


    • Applied fluid mechanics
    • Boundary layer and shear turbulence
    • Wakes
    • Power and plant engineering (mechanical engineering)
    • Other structures
    • Fluid mechanics and aerodynamics (mechanical engineering)
    • Elasticity (mechanical engineering)
    • Buckling and instability (mechanical engineering)
    • Fracture mechanics and hardness (mechanical engineering)
    • boundary layer turbulence
    • elasticity
    • fatigue
    • mechanical stability
    • offshore installations
    • wakes
    • wind turbines
    • medium fidelity loads modelling
    • nonneutral ABL stability conditions
    • wind turbine component fatigue loading
    • wake affected nonstationary flow fields
    • nonneutral atmospheric stability conditions
    • dynamic wake meandering model
    • atmospheric boundary layer stability
    • primary wake meandering dynamics
    • large turbulent scales
    • wake expansion
    • atmospheric boundary layer turbulence
    • classical Mann spectral tensor
    • buoyancy effects
    • nonstationary wind turbine inflow fields
    • fatigue loads
    • aeroelastic model HAWC2
    • Lillgrund offshore wind farm
    • WF
    • wind farm model validation
    • wake effects
    • tower load recordings
    • atmospheric boundary layer stability effects
    • rotating wind turbine components
    • unstable atmospheric boundary layer stratification


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