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Example Study Workflow

This example shows a realistic pyIECWind workflow where one input file generates multiple IEC wind-condition files for use with OpenFAST InflowWind.

Goal

Starting from a single .ipt file, we will:

  1. define multiple IEC cases
  2. generate a set of .wnd files
  3. understand how those filenames map into OpenFAST InflowWind usage

Input File

The shipped example file is:

examples/sample_case.ipt

Its Cases block currently requests:

ECD             True   [+R]                     - Extreme Coherent Gust with Direction Change
EWS             True   [V+12.0]                - Extreme Wind Shear
EOG             True   [R+2.0]                 - Extreme Operating Gust
EDC             True   [+R]                     - Extreme Direction Change
NWP             True   [23.7]                  - Normal Wind Profile
EWM             True   [50]                    - Extreme Wind Model

This means one run will expand into six output wind files.

Run The Study

Generate the files into a dedicated output folder:

pyiecwind run examples/sample_case.ipt -o outputs

Expected Output Files

For the current sample input, the generated filenames are:

outputs/ECD+R.wnd
outputs/EWSV+12.0.wnd
outputs/EOGR+2.0.wnd
outputs/EDC+R.wnd
outputs/NWP23.7.wnd
outputs/EWM50.wnd

What The Filenames Mean

Each filename directly reflects the expanded IEC condition code:

  • ECD+R.wnd: extreme coherent gust with direction change, positive direction, rated speed
  • EWSV+12.0.wnd: extreme vertical wind shear, positive shear, 12.0 user-unit hub-height speed
  • EOGR+2.0.wnd: extreme operating gust at rated speed plus modifier
  • EDC+R.wnd: extreme direction change, positive direction, rated speed
  • NWP23.7.wnd: normal wind profile at 23.7 m/s
  • EWM50.wnd: 50-year extreme wind model

This naming is useful in parametric studies because the resulting file already tells you which IEC case it represents.

How This Maps Into OpenFAST InflowWind

pyIECWind generates the wind input files themselves. OpenFAST still needs to be configured to point InflowWind at the desired .wnd file for a given simulation.

Typical usage pattern:

  1. generate a library of .wnd files with pyIECWind
  2. choose one case for a simulation run
  3. set the InflowWind wind-file path in your OpenFAST model to that .wnd file
  4. run OpenFAST for that case
  5. repeat for the other generated files

In practice, many users run a batch study where each OpenFAST case references one of the generated .wnd files.

Concrete InflowWind Example

For the examples/sample_case.ipt file, the sample turbine geometry is:

  • hub height: 150.0 m
  • rotor diameter / reference length: 240.0 m

If you want to run OpenFAST with one generated wind file such as:

outputs/EWM50.wnd

then the corresponding InflowWind section is typically set up as a uniform wind-file case, with the generated .wnd file referenced through Filename_Uni.

Illustrative snippet:

------- InflowWind INPUT FILE -------------------------------------------------------------------------
IEA 15 MW Offshore Reference Turbine
-------------------------------------------------------------------------------------------------------
False                  Echo            - Echo input data to <RootName>.ech (flag)
2                      WindType        - wind file type (2 = uniform wind file)
0.0                    PropagationDir  - Direction of wind propagation (deg)
0.0                    VFlowAng        - Upflow angle (deg)
False                  VelInterpCubic  - Use cubic interpolation for velocity in time
1                      NWindVel        - Number of points to output the wind velocity
0.0                    WindVxiList     - Inertial X coordinate list (m)
0.0                    WindVyiList     - Inertial Y coordinate list (m)
150.0                  WindVziList     - Inertial Z coordinate list (m)
================== Parameters for Uniform wind file [used only for WindType = 2] ======================
"outputs/EWM50.wnd"    Filename_Uni    - Filename of time series data for uniform wind field
150.0                  RefHt_Uni       - Reference height for horizontal wind speed (m)
240.0                  RefLength       - Reference length for linear horizontal and vertical shear (-)

Field Mapping

For a pyIECWind study using the current sample case:

  • Filename_Uni points to the specific generated wind file for the selected IEC case
  • RefHt_Uni should match the turbine hub height used in the .ipt file
  • RefLength should match the rotor diameter used in the .ipt file
  • WindVziList is commonly evaluated at hub height for a single-point velocity output example

This means that for the shipped example:

  • RefHt_Uni = 150.0
  • RefLength = 240.0

and Filename_Uni changes from case to case:

  • outputs/ECD+R.wnd
  • outputs/EWSV+12.0.wnd
  • outputs/EOGR+2.0.wnd
  • outputs/EDC+R.wnd
  • outputs/NWP23.7.wnd
  • outputs/EWM50.wnd

Batch Study Interpretation

In a batch OpenFAST study, you would normally keep the structural and controller model fixed and vary only the wind-file reference between runs.

For example:

  • Run 1 uses Filename_Uni = "outputs/ECD+R.wnd"
  • Run 2 uses Filename_Uni = "outputs/EWSV+12.0.wnd"
  • Run 3 uses Filename_Uni = "outputs/EWM50.wnd"

That is the practical bridge between one pyIECWind case-definition file and a family of OpenFAST simulations.

Why This Is Useful

This workflow gives you:

  • one human-readable source file for a study
  • multiple deterministic .wnd outputs
  • filenames that preserve the IEC case identity
  • a clean bridge from IEC case definition to OpenFAST batch execution

Variations

A few common extensions of this workflow are:

  • adding multiple NWP wind speeds in one file, such as [10.0, 14.0, 23.7]
  • adding both EWM50 and EWM01
  • creating separate .ipt files for parked, operating, and verification studies

Related Documentation