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    Simulation and analysis of wind turbine loads for neutrally stable inflow turbulence

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    ChungwookSim_Master_Thesis_Civil_Summer09.pdf (11.87Mb)
    Date
    2009-08
    Author
    Sim, Chungwook
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    Abstract
    Efficient temporal resolution and spatial grids are important in simulation of the inflow turbulence for wind turbine loads analyses. There have not been many published studies that address optimal space-time resolution of generated inflow velocity fields in order to estimate accurate load statistics. This study investigates turbine extreme and fatigue load statistics for a utility-scale 5MW wind turbine with a hub-height of 90 m and a rotor diameter of 126 m. Load statistics, spectra, and time-frequency analysis representations are compared for various alternative space and time resolutions employed in inflow turbulence field simulation. Conclusions are drawn regarding adequate resolution in space of the inflow turbulence simulated on the rotor plane prior to extracting turbine load statistics. Similarly, conclusions are drawn with regard to what constitutes adequate temporal filtering to preserve turbine load statistics. This first study employs conventional Fourier-based spectral methods for stochastic simulation of velocity fields for a neutral atmospheric boundary layer. In the second part of this study, large-eddy simulation (LES) is employed with similar resolutions in space and time as in the earlier Fourier-based simulations to again establish turbine load statistics. A comparison of extreme and fatigue load statistics is presented for the two approaches used for inflow field generation. The use of LES-generated flows (enhanced in deficient high-frequency energy by the use of fractal interpolation) to establish turbine load statistics in this manner is computationally very expensive but the study is justified in order to evaluate the ability of LES to be used as an alternative to more common approaches. LES with fractal interpolation is shown to lead to accurate load statistics when compared with stochastic simulation. A more compelling reason for using LES in turbine load studies is the following: for stable boundary layers, it is not possible to generate realistic inflow velocity fields using stochastic simulation. The present study presents a demonstration that, despite the computational costs involved, LES-generated inflows can be used for loads analyses for utility-scale turbines. The study sets the stage for future computations in the stable boundary layer where low-level jets, large speed and direction shears across the rotor, etc. can possibly cause large turbine loads; then, LES will likely be the inflow turbulence generator of choice.
    Department
    Civil, Architectural, and Environmental Engineering
    Description
    text
    Subject
    utility-scale wind turbine
    neutral atmospheric boundary layer
    inflow turbulence
    Large-Eddy Simulation
    stochastic simulation
    fractal interpolation
    extreme and fatigue load statistics
    wind turbine loads
    URI
    http://hdl.handle.net/2152/ETD-UT-2009-08-387
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    University of Texas at Austin Libraries
    • facebook
    • twitter
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    • youtube
    • CONTACT US
    • MAPS & DIRECTIONS
    • JOB OPPORTUNITIES
    • UT Austin Home
    • Emergency Information
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    • Web Accessibility Policy
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    • Adobe Reader
    Subscribe to our NewsletterGive to the Libraries

    © The University of Texas at Austin