Wind fields from file

1. IECWind fluctuating three component wind

For the IECWind fluctuating 3-component wind, only the fluctuating part of the wind is given in the wind input files. The mean wind speed given as input and is added to the yield the total wind velocity in the longitudinal direction. The input files must conform to the 3-dimensional 3-component wind time series from the rectangular IEC format (See Thomsen, K., 2006. Mann turbulence for the IEC Code Comparison Collaborative (OC3). Risø National Laboratory). More specifically they must include time series of wind velocity in binary format, with a 3-dimensional array having indices in vertical direction running fastest, then indices in lateral direction and indices in longitudinal direction running slowest.

2. TurbSim fluctuating three component wind

The wind field domain- and field size are extracted from the TurbSim .sum file. The wind field domain location in the global coordinate system is not given explicitly by the user. The vertical position of the wind field center is the same as in TurbSim; i.e. taken as the hub height given on the turbsim .sum file. Horizontally, the wind field is positioned around the global origin, but with a half grid width downwind of the origin. Since the TurbSim wind is non-periodic, this is necessary to ensure that the entire turbine lies in the same part of the wind field at the start of the simulation. The wind at the global origin will thus not start at the first slice.

The wind field must be large enough to ensure that the whole structure is within the wind field during the entire simulation. As the TurbSim wind field is nonperiodic, the beginning and end of the wind field will not fit together.

3. Fluctuating two component wind from text file

Wind speed and direction is read from a text file provided as input. The text file should be on the following format:

  • Line 1 : Number of samples

  • Line 2 : Time step

  • Line 3 : Number of columns (=2)

  • Line 4.. : velocity and direction

The file head may contain an arbitrary number of comment lines starting with '.

Example:

  2048       ' Number of samples \
' Comment line 1                  \
  .50        ' Time step           \
  2          ' Format type     **Head of file**
' Comment line 2                   /
' Comment line 3                  /
' Last comment line              /
  20.0000      180.000
  20.3923      180.500
  20.7822      181.000
  21.1672      181.500
  21.5451      182.000
   .
   .

The time step given on the ASCII file may be different from the time step used in the simulation. The specified wind time series will be re-sampled using the time step applied in the simulation based on linear interpolation. Further the velocities will be scaled by the square root of the scaling factor.

If the read time series is shorter than the length of the simulation, the wind velocity in the last part of the simulation will be set to zero.