FAST Response to FF .wnd File Generated by GH Bladed


I am using FAST to try and match the GH Bladed response of a turbine. I have been provided the Bladed generated .wnd and results files. I have been trying to read the .wnd file into Matlab with a modified version of the readBLgrid.m script but the byte arrangement of the binary header file appears different. Does anyone have any recommendations?

Ryan Neahr

Hi, Ryan.

Do you know what version of GH Bladed was used to generate the wind file, and what type of turbulence was used (e.g., Mann model?)?

Hi Bonnie,

The turbulent file was generated with code version 3.85 of Bladed using the Kaimal model.


Hi Ryan.

I have Bladed 3.81, so I can’t verify that the format hasn’t changed. But, you also said you are using a “modified version of readBLgrid.m” What exactly is modified?

Hi Bonnie,

Initially I commented out the section pertaining to the summary file since one did not exist. Through trial and error, I changed the byte arrangement until the end of the file was reached after the entire 4-D matrix was loaded. The Bladed project file provided the grid size and the number of time steps so I was confident in the dimensions of the matrix. I then used a Matlab script from the forums to reconstruct the .wnd file in the format necessary for FAST. Using the ReadBLGrid script as a guide I manually changed a summary file to match the known characteristics of the Bladed wind file (i.e. hub height, grid spacing, etc). From the Bladed output I have the time series horizontal wind direction and magnitude at hub height. FAST was able to match the horizontal wind direction and magnitude from Bladed fairly well (posted below).

I have not had a chance to dig through Aerodyn to understand the values within the summary file which must be updated. Can you provide any recommendations?

Do you foresee any other issues with this approach?

Ryan Neahr

Hi Ryan,

The InflowWind archive (also found in the Source/InflowWind folder of the AeroDyn v13.00.01a-bjj archive) contains a file describing the summary file information necessary to read the Bladed-Style FF wind files in AeroDyn. It’s called Format_FF_Sum_File.pdf

I am still somewhat surprised that you had to modify the script to read the binary file, but it sounds like you were able to extract all the information you needed.

There are a couple of things I’d make sure to check:

  1. Shear: AeroDyn doesn’t automatically add shear (except in the HWC wind files that are still undocumented), and I don’t think the Bladed files add the shear. So, you’ll need to add it somewhere, probably when you reconstruct the file as you mentioned.
  2. Clockwise flag: This flag in the summary file was originally added to compare Bladed and FAST. It is my understanding that Bladed read (or generated) the files based on the direction of rotor rotation. I’m not sure this is still true, but the feature still exists in AeroDyn/InflowWind. So, you should check to see if the grid starts on the right or left (right now I can’t remember which is which…but I seem to recall another forum post where the Clockwise flag had to be set opposite its expected value…). You may have a mirror image of the wind file otherwise.