Dear @Kepa.Cueto ,
I’m guessing this is tied to small nonlinearities in what is normally the linear part of the lift curve, e.g. as discussed in the following forum topic and OpenFAST issue on GitHub:
Hi everyone,
I have a question on the unsteady aerodynamic (dynamic stall) model.
Currently, I am running stand-alone AeroDyn test cases to get to know the tool and how it works.
I’ve noticed that activating the UA model causes a drop in Cl and as a result a drop of the predictid AeroPwr.
The BEM part should be fine, becaues the converged AOA and induction coefficients are not affected by switching UA on.
My initial guess was that is should be due to worng dynamic stall parameters (which ar…
opened 08:14PM - 26 May 20 UTC
bug
I would normally expect the unsteady airfoil aerodynamics (UA) model of OpenFAST… / AeroDyn to influence the variations of lift about the mean, but not to directly influence the mean lift itself. However, Mehran Saeedi on our forum noticed that the mean lift is being impacted for some airfoils, e.g., the DU25 airfoil in the NREL 5-MW baseline models--see the figure below.
This is likely the result of inconsistencies between the UA parameters and the the static airfoil data in the AeroDyn v15 airfoil data file. **These inconsistencies should be fixed in the sample OpenFAST models provided in the r-test.** I'm not sure where the UA parameters originated from for all airfoils, but I would guess a mistake was made when the AeroDyn v15 airfoil data input files were first made, at least for some airfoils.
I know that there are scripts floating around that can be used to derive the UA parameters from the static airfoil data. It would be great if these scripts could be used to update the AeroDyn v15 airfoil data files.
For more information, see the related discussion on the forum: https://wind.nrel.gov/forum/wind/viewtopic.php?f=2&t=2492.
opened 11:17AM - 16 Dec 21 UTC
closed 01:51PM - 17 Dec 21 UTC
Type: Bug
Module: AeroDyn
Hi everyone,
I wrote here mounths ago and I solved successfully the problem, so… I try again with another issue.
I'm analyzing the behavior of a 5MW off-shore wind turbine in steady condition ( no tilt angle, no motion added), with the OpenFast 2.6 version. If I compute the problem using AFAeroMod=1, the result is coherent with my expectations. If I use AFAeroMod=2, even though the problem is still in steady condition, the result is not the same as before in terms of power and thrust.
I've checked Lift and Drag coefficients and they are quite different between the two cases.
Why the two cases don't give the same results?
Is it possible that there is a sort of bug in AFAeromod when the case is steady?
Hoping to be clear enough, thank you in advance.
Best regards,
1 Like