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The Science of Making Torque from Wind (TORQUE 2018)

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Room: BL.28 Carassa e Dadda
Chaired by: Jens Nørkær Sørensen | DTU
Topic: WWT. Wind, Wakes and Turbulence
Form of presentation: Oral
Duration: 90 minutes

Authors:
Sara C. Pryor, Rebecca J. Barthelmie, Andrea N. Hahmann, Tristan J. Shepherd, Patrick Volker

Abstract:
High-resolution numerical simulations of the effects of wind turbines on regional climate are presented for a domain centered on the highest density of current wind turbine deployments in the contiguous US. Resulting analyses indicate that impacts on temperature, specific humidity, precipitation, sensible and latent heat fluxes are statistically significant only in summer, are of very small magnitude and are highly localized. Our research implies that further expansion of wind turbine deployments can likely be realized without leading to substantial downstream impacts on weather and climate.

Authors:
Søren Juhl Andersen

Abstract:
An important area of wind farm aerodynamics concerns the control of individual turbines and how the flow changes through the induction zone as it approaches a wind turbine. Recent studies comprise steady state consideration by Troldborg and Forsting 2017 and the change in the low frequency part of the spectra by Mann et al. 2017. Another area investigates the intentional control of wind turbine wakes to avoid the unfavorable wake effects and to optimize the total power production of the farm, as \textit{e.g.} the idea of yawing the first turbine by Gebraad et al. 2016. The aforementioned studies have generally focussed on steady state or at least low frequency changes. This study aims to investigate the instanteneous and mutual interaction between flow and turbine to address how correlated the turbine response is to the turbulent inflow and, inversely, how does the incoming turbulence change due to the turbine response. This interaction is investigated numerically using a fully coupled LES and aeroelastic framework.

Authors:
Giacomo Valerio Iungo, Stefano Letizia, Lu Zhan

Abstract:
Quantification of the aerodynamic forcing exerted by utility-scale wind turbines on the atmospheric boundary layer for different turbine settings and atmospheric stability conditions is one of the greatest challenges to overcome in order to achieve accurate predictions of wind turbine wakes. Numerical simulations of wind turbine wakes are typically performed by means of tabulated data of the blade geometry and aerodynamic coefficients, which are typically proprietary data and not publicly available for real wind turbines. In order to achieve enhanced accuracy in the quantification of the aerodynamic forcing exerted by utility-scale wind turbines for different atmospheric stability conditions and turbine settings, the axial induction at the rotor disk is quantified by coupling LiDAR wake measurements with RANS simulations. LiDAR measurements, collected for an onshore wind farm located in North Texas, are analyzed through the control volume approach of the mass conservation and the streamwise momentum. The turbulent stresses are quantified through a mixing length model, while the pressure field is iteratively estimated through the RANS solver. This approach allows quantifying the axial induction at the rotor disc as a function of the radial distance from the hub for different incoming wind speed and atmospheric stability regimes.

Authors:
Gunner C. Larsen

Abstract:
The purpose of this study is to improve the predictive capability of the DWM model generalized to non-neutral ABL stability conditions. The emphasis is on rotating wind turbine components, and the improvement is intimately linked to a newly developed refinement of classic Monin-Obukhov theory, which is primary resulting in less pronounced mean wind shear outside the surface layer, where most modern wind turbines are operating. The model improvements are validated against a huge set of full-scale data, which allows for a one-to-one comparison of wind turbine load simulations and measurements conditioned on ABL stability condition.

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