FAST: tail furl input file

Hello everyone,

I am simulating a small turbine that uses a tail plate (fin) to keep its rotor aligned with the wind at all wind speeds. Thus the turbine is not actually a furling turbine, but I use the furling file in order to include the tail vane in my model (setting both TailFurl and RotFurl flags to false).

The tail geometry is as simple as it gets: the plate (fin) is vertical and has no angle with the rotor main axis (assuming there is no tilt). Does this mean that “TFrlTilt” should be 0 or should it be 90? (I am reasonable certain that “TFrlSkew” should be set to 0)

I have looked at figure 17 in the FAST manual but I can’t really figure it out. And I have also tried looking at the results, running my simulations with “TFrlTilt” = 90 and 0, but I cannot see any significant difference [this is also puzzling me].

Best wishes,

Dear Thanos,

If you have no furling hinge DOFs (implying that RFrlDOF and TFrlDOF are both False), you should set the initial furling angles (RotFurl and TailFurl) to zero and then the furling hinge locations (RFrlPntxn, RFrlPntyn, RFrlPntzn and TFrlPntxn, TFrlPntyn, TFrlPntzn) and orientations (RFrlSkew, RFrlTilt and TFrlSkew, TFrlTilt) will have no effect on the simulation results.

Instead, in order to define the tail fin aerodynamic properties, you only need to define the location of the tail fin center of pressure (TFinCPxn, TFinCPyn, TFinCPzn) and the orientation of the tail fin chordline and plane (TFinSkew, TFinTilt, TFinBank). Figure 19 in the FAST manual (for v6.0) is what you need to examine here. For example, if the tail fin chordline is parallel with the shaft axis, which has no skew or tilt, and the plane is vertical, you should set TFinSkew, TFinTilt, and TFinBank all to zero.

I hope that helps!

Best regards,

Dear Jason Jonkman,

This certainly did help! :slight_smile: Thanks.

Best wishes,

i am trying to simulate a small wind turbine with tail_furling.
I just want to ask a question for the tail fin skew, to know if it is correct what i have understood so far.
In the picture you can see a draft of the geometry.
From the info of the structure, i know the geometry (center of mass, 0 fin tilt) in the condition that is shown in the picture, where is normally the up stop of the tail.
So my question is, is it right to put a tail_fin_skew of -20 ?

Then i want to put the up stop in 90 deg from the rotor, is it right to have all the inputs the same as before (same xyz and skew), and just put the up stop in TFrlUSSP -20 deg ?

Thank you in advance, hope i wrote something enough understandable

Dear Gerasimos,

The tail boom and fin in FAST v7 should be specified at a tail-furl angle of zero. My understanding is your picture shows the tail at the upstop position of 20 degrees. So, I presume the tail would under normal situations be oriented perpendicular to the rotor (at the downstop position) at a tail-furl angle of zero. Thus, I would expect that you’d set TFinSkew = 0, TFrlDSSP = 0, and TFrlUSSP = 20.

I hope that helps.

Best regards,

Dear Jason,
thanks for your reply,

a) In normal situation, i didn’t mention that the tail is as shown in the first draft, so at the fully furled position is as shown in this draft (not a real wind direction).
So for this condition i set
20 TFinSkew
0.0 TFrlUSSP
-100.0 TFrlDSSP (10 degrees from the rotor)

b) Then i want to simulate another situation when the tail in normal position is perpendicular to the rotor, and it furls in the same direction as before, as shown in this draft. so i now have

20 TFinSkew
-20.0 TFrlUSSP
-100.0 TFrlDSSP (10 degrees from the rotor)

Thank you in advance

Dear Gerasimos,

I’m sorry, but I don’t understand what you are saying and cannot comment on it.

Best regards,

Hi, I am simulating a small wind turbine with the help of FAST software
This turbine contains a tail that makes it wind direction (I emphasize that the job of this tail is just to put the turbine in the wind direction and does not include any special technology)

Now my question is whether it is necessary for this turbine to fill the inputs of the furl file and if necessary wich parameters should be set and wich parameters don’t need to be set?

Dear Ali,

If you want to model the tail in FAST, “yes”, you’d need to use the furling input file, which is where the tail properties are set. This means that you’ll need to use FAST v7 (rather than FAST v8 or OpenFAST). Which inputs are important to set in the furling input file depends on the wind turbine configuration and if you have hinges (what are called rotor-furl and tail-furl in FAST). Certainly, inputs such as the tail boom/fin mass, center of mass, and inertia, and tail-fin aerodynamic properties are all important.

Best regards,

Thank you for your answer
But there were a few more questions for me

  1. Can’t FAST V8 be used for this?

  2. Can you specify exactly what parameters I need to set(for modelling simple tail plate for being in wind directions) and what parameters do not need

Dear Ali,

No, the tail functionality of FAST v7 has not yet been migrated into FAST v8 or OpenFAST yet. Actually, I just found out yesterday that NREL now has funding to introduce the tail and furling function into OpenFAST (likely based on the model available in FAST v7. This work has not started yet, but should be completed within the next year. Until then, you’ll need to revert back to FAST v7 (or modify the source code yourself).

I feel like I already answered your second question. If you are not already familiar, I suggest reviewing the tail modeling inputs available in FAST v7 by reviewing the old FAST User’s Guide: … d91gg/view.

Best regards,

I also have a few questions about the Elastodyn module

  1. Activation of each degree of freedom in the DEGREES OF FREEDOM section What effect in the simulation?
    2- I want to simulate a small wind turbine that includes a tail (just to place the turbine in the wind direction) but I have trouble finding the center of mass of the nacelle Because I do not know whether to consider the turbine tail as a member of Nacelle or not?(I ask this question for the NacCMxn parameter, because if I calculate the nacell by calculating the tail plate and tail-boom, I get a point for the center of mass, and if I do not count the tail-boom and the tail plate as a member of the nacelle, another point is obtained).

Dear Ali,

Here are my answers to your questions:

  1. Enabling DOFs introduces structural flexibility and aero-elastic effects in the model. With more DOFs enabled, there will be more natural frequencies in the model that can interact with excitation frequencies. You can always run multiple simulations with different DOFs enabled to see there effect. The goal should always be to enable DOFs that are important for capturing the quantities of interest that you want to capture. Typically this involves enabling DOFs that have natural frequencies in the range of excitation frequencies from the rotor rotation and aerodynamic loads e.g., to model all natural frequencies up to nine harmonics of the rotor speed (9P).
  1. If you specify the tail boom or tail fin mass independently from the nacelle mass, then the center of mass of the nacelle should be the mass center without the tail If you cent the tail boom and tail fin masses to zero, then the nacelle mass and center of mass should be set to that of the nacelle plus tail.

Best regards,