Abstract
Abstract. The interaction between wind turbines through their wakes is an important aspect of the conception and operation of a wind farm. Wakes are characterized by an elevated turbulence level and a noticeable velocity deficit, which causes a decrease in energy output and fatigue on downstream turbines. In order to gain a better understanding of this phenomenon this work uses large-eddy simulations together with an actuator line model and different ambient turbulence imposed as boundary conditions. This is achieved by using the Simulator fOr Wind Farm Applications (SOWFA) framework from the National Renewable Energy Laboratory (NREL) (USA), which is first validated against another popular Computational Fluid Dynamics (CFD) framework for wind energy, EllipSys3D, and then verified against the experimental results from the Model Experiment in Controlled Conditions (MEXICO) and New Model Experiment in Controlled Conditions (NEW MEXICO) wind tunnel experiments. By using the predicted torque as a global indicator, the optimal width of the distribution kernel for the actuator line is determined for different grid resolutions. Then, the rotor is immersed in homogeneous isotropic turbulence and a shear layer turbulence with different turbulence intensities, allowing us to determine how far downstream the effect of the distinct blades is discernible. This can be used as an indicator of the extents of the near wake for different flow conditions.
Highlights
An important aspect for the conception of wind farms is the turbine spacing, which depends on the interaction of wind turbines through their wakes
This work will apply the actuator line method (ALM) in order to model the transient behaviour of the rotor by representing distinctly the rotating blades as presented by Troldborg (2009)
Each blade is represented by a force line allowing us to reproduce the helicoidal vortical structure in the near wake and allowing us to assess its interaction with the flow
Summary
An important aspect for the conception of wind farms is the turbine spacing, which depends on the interaction of wind turbines through their wakes. This phenomenon can decrease the wind park energy output by up to 20 % due to the velocity deficit propagated by the wakes (Manwell et al, 2010). This work will apply the actuator line method (ALM) in order to model the transient behaviour of the rotor by representing distinctly the rotating blades as presented by Troldborg (2009). Each blade is represented by a force line allowing us to reproduce the helicoidal vortical structure in the near wake and allowing us to assess its interaction with the flow
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