openfast Feature request: Run FAST.Farm without wind

Is your feature request related to a problem? Please describe. It would be useful to be able to run FAST.Farm without environmental loads to find the equilibrium position of floating systems with shared moorings or to consider waves only. We can disable the waves with WaveMod=0 in SeaState but we cannot do something similar for the wind when using FAST.Farm.

Describe the solution you'd like It would be nice to have an option ModWake=0 to skip the wake calculations and Mod_AmbWind=0 to remove the ambient wind (though the later could be achieved with WindType=1 and HWindSpeed=0 in InflowWind).

Describe alternatives you've considered I have tried different combinations of zero/low wind speed with different AeroDyn configurations but they all fail for some reason. For example, I get the following after a few seconds if I try zero wind speed in InflowWind and Wake_Mod=0 in AeroDyn:

Dec 17 '24 23:12 lucas-carmo

I don't know if we will be able to get this into v 4.0, but we can probably add it to a 4.1 or the 5.0 (whichever comes first).

Dec 17 '24 23:12 andrew-platt

I agree that this may be useful feature to add, but it may not be as trivial as suggested given that much of FAST.Farm revolves around coupling the wind turbines of a wind farm together through wind/wakes.

This topic was actually discussed recently on our forum: https://forums.nrel.gov/t/fast-farm-without-wind-modelling-setup/7080, where to avoid the +/- pi/2 error, a workaround was proposed involving:

Set up the FAST.Farm simulation with a low steady wind speed, low rotor thrust, and no wind turbine control
To set steady wind speed, use Mod_AmbWind = 2 with WindType = 1 in InflowWind
To reduce the rotor thrust, reduce the chord (BlChord) and aerodynamic lift and drag coefficients in AeroDyn
To avoid numerical issues in AeroDyn, set WakeMod = 0, AFAeroMod = 1, TwrPotent = 0, TwrShadow = 0, and TwrAero = FALSE.
To disable wind turbine control, set CompServo = 0 in OpenFAST
Set a low value of NumPlanes (e.g., NumPlanes = 2) in FAST.Farm to ensure that there are no wake effects between the turbines

Best regards,

Dec 17 '24 23:12 jjonkman

Thanks, @jjonkman! I had tried those configurations but did not reduce the chord, lift, and drag coefficients. That should do the trick!

Best,

Dec 17 '24 23:12 lucas-carmo