I have a doubt that I would like to share with you.
I am trying to perform some simulations using FAST.Farm that include yaw misalignment.
I have read from literature that the power loss introduced by misaligning the rotor relatively to the inflow with an angle gamma follows the following relation
The values of the exponent Pp that I found in literature always lie between 1.8 and 3 (for instance, in the default FLORIS .json input file for the NREL 5MW this value is 1.88).
When trying to estimate this coefficient using FAST.Farm, I always obtain the value 3 (with steady inflow conditions and the Pitt/Peters skewed inflow model). As I understood, this is the value to be expected from a standard BEM code.
The relatively high value for the exponent Pp is giving me a hard time to apply wake steering for power maximization in FAST.Farm, since the power losses introduced by yawing a turbine are quite high.
I am not sure whether the value of Pp=3 is realistic. Could maybe things be improved by tuning the input files, such as Aerodyn?
Thanks for the attention.