PhD Project: Wind Turbine Wake in Atmospheric Turbulence

  • Rethore, Pierre-Elouan (Projektdeltager)

    Projektdetaljer

    Beskrivelse

    This thesis describes the different steps needed to design a steady-state
    computational fluid dynamics (CFD) wind farm wake model. The ultimate
    goal of the project was to design a tool that could analyze and extrapolate
    systematically wind farm measurements to generate wind maps in order to
    calibrate faster and simpler engineering wind farm wake models. The most
    attractive solution was the actuator disc method with the steady state k-ε
    turbulence model.
    The first step to design such a tool is the treatment of the forces. This
    thesis presents a computationally inexpensive method to apply discrete body
    forces into the finite-volume flow solver with collocated variable treatment
    (EllipSys), which avoids the pressure-velocity decoupling issue.
    The second step is to distribute the body forces in the computational
    domain accordingly to rotor loading. This thesis presents a generic flexible
    method that associates any kind of shapes with the computational domain
    discretization. The special case of the actuator disc performs remarkably
    well in comparison with Conway’s heavily loaded actuator disc analytical
    solution and a CFD full rotor computation, even with a coarse discretization.
    The third step is to model the atmospheric turbulence. The standard
    k-ε model is found to be unable to model at the same time the atmospheric
    turbulence and the actuator disc wake and performs badly in comparison
    with single wind turbine wake measurements. A comparison with a Large
    Eddy Simulation (LES) shows that the problem mainly comes from the
    assumptions of the eddy-viscosity concept, which are deeply invalidated in
    the wind turbine wake region. Different models that intent to correct the
    k-ε model’s issues are investigated, of which none of them is found to be
    adequate. The mixing of the wake in the atmosphere is a deeply non-local
    phenomenon that is not handled correctly by an eddy-viscosity model such
    as k-ε .
    StatusAfsluttet
    Effektiv start/slut dato01/10/200613/12/2009

    Emneord

    • 2009 DCE Ph.d projects
    • Wind Farm
    • Wind Turbines
    • Turbulence

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