Turning off Unsteady Aerodynamics for cylinder airfoil

Wind & Water Rotor Aerodynamics
1

Hi everyone,

I am working with the WP Baseline model (OpenFast 3.1.0) and I keep getting the following warning:

Warning: Turning off Unsteady Aerodynamics because UA parameters are not included in airfoil
(airfoil has likely has constant polars). (node 1, blade 1)

The warning appears for node 1 and 2 of every blade and I noticed that this is the cylindrical airfoil.
I use the default cylinder.dat file which has its UA parameters just like the other airfoils of the model. The UA parameters of the cylinder airfoil are not written into the UA.sum file (they are all zero).

Makes sense to me that the cylinder has constant polars but in my understanding, the turbulences behind the cylinder should have an influence on e.g. the drag force of the cylindrical blade part compared to laminar flow.

So here are my questions:

  1. Is the UA module just turned off for the cylinder airfoil or for all airfoils?
  2. If UA is turned off for the cylinder, is the stall of it still taken into account (even if it does not change over the angle of attack)?
  3. Is there a way to enable UA for the cylinder airfoil?

Thanks a lot and Best Regards!

2

Dear Jakob,

Here are my answers to your questions:

  1. These warnings are expected for cylindrical airfoil sections because the UA model is not valid for cylinders, which have no lift. The warnings will also appear for other airfoil sections if the angle of attack exceeds UACutOut.

  2. Yes, drag is still considered for a cylindrical airfoils.

  3. The UA model of AeroDyn is based on the lift curve, so, an airfoil with no lift cannot have UA enabled.

Best regards,

3

Hi Jason,
Thanks a lot for answering my questions!