Wind fields from file

1. IECWind fluctuating three component wind

For the IECWind fluctuating 3-component wind (Mann turbulence), 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, and also HAWC2 v13.1, 2024. Release Notes: Mann Turbulence box - read in wrong direction. DTU Wind Energy). 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.

Required input for wind components is:

Direction

Mean wind direction

Mean Speed

Mean wind speed

Vertical Coordinate

N input z-coordinates for scaling of mean wind speed and fluctuating wind

Mean Speed Factor

N scaling factors for mean wind speed, to define shear profile

Longitudinal Velocity Factor

N scaling factors for height-dependent scaling of longitudinal component of fluctuating wind

Lateral Velocity Factor

N scaling factors for height-dependent scaling of lateral component of fluctuating wind

Vertical Velocity Factor

N scaling factors for height-dependent scaling of vertical component of fluctuating wind

Longitudinal File Name

File containing longitudinal component of fluctuating wind

Lateral File Name

File containing lateral component of fluctuating wind

Vertical File Name

File containing vertical component of fluctuating wind

Required input for orienting the wind domain in the global reference frame is:

Lower left position

(X, Y, Z) coordinates (in a wind aligned system) of the data point at the front lower left (looking upstream) of the domain

Wind field domain size

Number of data points in the longitudinal (NX), lateral (NY), and vertical (NZ) directions

Wind field size

The field lengths in the longitudinal (LX), lateral (LY), and vertical (LZ) directions, defined such that the spacing between data points is given by D[X,Y,Z] = L[X,Y,Z] / N[X,Y,Z].

Required inputs to specify how turbulence files are read from file, and advected through the domain:

Number of slices

Number of wind cross-sectional planes (slices) to load from file into memory

Reverse box

Specify if turbulence is advected from end of file to start of file (default) or in reverse order (legacy).

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.

Required input is:

Direction

Mean wind direction

Wind File Name

.bin file containing wind field

Sum File Name

.sum file containing wind field summary

Number of Slices in Memory

Number of wind slices read (default value is \(800\))

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.

Required input is:

File Name

File with wind field definition