Comparison of wind farm large eddy simulations using actuator disk and actuator line models with wind tunnel experiments

- Comparison of actuator disk and actuator line model LES with wind tunnel measurements.
- Detailed documentation of used comparison methodology.
- Modeling of turbine tower and nacelle in relatively coarse grid LES.
- Use of blade element analysis to obtain power and thrust curves for ALM model.
- Representation of experimentally observed turbulent boundary layer pro_les in LES.

We compare wind farm large eddy simulations with the EPFL wind tunnel measurement by Chamorro and Porté-Agel (Bound-Lay. Meteorol. 136, 515 (2010) and Energies 4, 1916 (2011)). We find that the near turbine wake, up to 3 turbine diameters downstream, of a single turbine is captured better with the actuator line method than using the actuator disk method. Further downstream the results obtained with both models agrees very well with the experimental data, confirming findings from previous studies. For large aligned wind farms we find that the actuator disk model predicts the wake profiles behind turbines on the second and subsequent rows more accurately than the wake profile behind the first turbine row. The reason is that the wake layer profile that is created at hub height in very large wind farms is closer to the assumptions made in the actuator disk model than the logarithmic profile found in the inflow conditions. In addition, we show that, even in relatively coarse resolution simulations, adding the effect of the turbine nacelle and tower leads to a significant improvement in the prediction of the near wake features at 1 and 2 diameters downstream.