Hello everyone,
I’m reaching out because I’m encountering an issue with FAST.Farm (version FAST.Farm-v4.0.4-dirty). I’ve reduced the number of radial output points to 7 and set the downstream distance to 1 diameter (284 m, using the IEA 22 MW model). However, the output columns for the following variables are filled with zeros:
Has anyone experienced this before, or could you suggest potential causes (e.g., configuration, version-specific issues)? Any guidance would be greatly appreciated!
Thank you in advance for your help.
Dear @Tom.Salic,
Perhaps you have not run FAST.Farm long enough and the wake has not yet propagated 284 m?
Best regards,
Dear @Jason.Jonkman,
Thank you for your suggestion. That was actually my first thought, so I ran the simulation for 1800 seconds with a mean wind speed of Umean=8 m/s. Under these conditions, the wake should theoretically have had enough time to propagate across the full 284 meters of the domain.
I’m running a simulation in FAST.Farm with an upstream turbine (T1) located 1000 meters away from the domain. However, I notice that at t=1, the wake is already visible across the domain in the first VTK file, even though physically, the wake should take about 125 seconds to propagate 1000 meters at a mean wind speed of 8 m/s.
From what I understand, FAST.Farm often uses a quasi-steady approach where the wake is calculated as an established (steady-state) field at each time step, rather than simulating its real-time propagation from t=0. This means the wake is effectively “projected” instantaneously across the domain, as if the turbine had been operating for a long time.
Is this behavior expected when using the quasi-steady wake model in FAST.Farm? Does the model intentionally initialize the wake field in this way, or could this indicate a misconfiguration?
attached is an image of the velocity field on the oxy plane for t=6 seconds
Best Regards,
I’ve found the source of my confusion—I was using Mod_Wake = 2 (curl-based model), which doesn’t provide access to the grid nodes in the way I expected.
Apologies for the unnecessary post, and thanks to those who might have started looking into it. Have a great day!
Best regards,
Dear @Tom.Salic,
I agree that when Mod_Wake = 2 (curled wake), FAST.Farm cannot output wake deficits at radial nodes; this limitation exists because the curled wake model is solved in rectangular coordinates rather than polar coordinates. Switching to Mod_Wake = 1 (polar wake) will solve this issue. If you want to see the wake deficit at each wake plane for any Mod_Wake setting, set OutAllPlanes = TRUE.
Regarding your other comment: FAST.Farm is initialized at time zero with 2 wake planes and adds a wake plane each low-resolution time step up until NumPlanes is reached. So the wake will continue propagating downstream until simulation time = DT_Low * ( NumPlanes - 2 ). FAST.Farm does not initialize with an established steady-state wake.
Best regards,
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