How Bladed calculates the rotor average wind speed?
Bladed versions affected: all Bladed versions supporting rotor average wind speed and direction.
Date of last article update: 13 March 2023
Bladed calculates the average wind speed over the rotor according to below figure. The rotor is discretized into several smaller areas where the wind speed at each of it is extracted from the field. The discretization is performed as a function of the rotor radius, i.e., the larger the rotor the larger number of smaller areas become (the size of each small area is constant). This is done to ensure that the rotor is discretized properly regardless of the rotor size. A minimum discretization of 3 is set when dealing with a very small rotor. The average wind speed (and direction) is then applied by averaging the values obtained from all smaller areas, see below figure for more detail.
The following table shows all the assumptions made when calculating the average wind speed and direction.
----------------------------------------------------------------------------------------
Considered effects when calculating the rotor average wind speed and direction
----------------------------------------------------------------------------------------
Effects | Included?
----------------------------------------------------------------------------------------
Turbulence | Yes
Tower shadow | No
Upstream wake | Yes
Yaw rotation | Yes
----------------------------------------------------------------------------------------