TwrBsMxt and TwrBsFxt for FAST 7 and FAST 8 not equal

Wind & Water Structural Analysis
1

Hello Jason,

I am trying to compare a FAST v7.02 and FAST v8.16. model to ensure they are the same (converted with your matlab functions). Giving turbulent wind (exactly same files) to the two models having the same configurations in the input files, results in differences in the tower base force of ~16% of the tower base force calculated by FAST7, if all components are flexible (except TeetDOF=0). (Same for tower base moment)

Is there any change in the calculation of the tower base moment and force or maybe in the blade moment calculation, that could cause this difference?
I couldn’t really find anything in the ‘ReadMe.pdf’.

Best regards,
Fiona

2

Dear Fiona,

I would not expect large differences between FAST v7 and FAST v8 unless you’ve enabled functionality that is not available in the other version.

I’m not sure what is causing differences in your case, but I would suggest simplifying the model to debug e.g. by disabling structural DOFs and/or control, and/or simplifying the aerodynamic options.

Best regards,