NREL 5MW with swept blades crashes FAST v8.15.00a-bjj

Hello Community,

I am trying to adjust the definition of the NREL 5MW baseline onshore turbine by adding prebent and sweep to the blades. I am using Test26.fst from CertTest as my reference setup. When I add just some prebent to the aeroDyn blade file and the beamDyn file, everything works perfectly. However, if I apply sweep my simulations will always crash with the following error message:

FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:BEMT_UpdateStates(node 17, blade2):BEMT_UnCoupledSolve:DeterminePhiBounds:There is no valid value of phi for these operating conditions!  Vx = -0.34787, Vy = 75.503, rlocal = 58.9, theta = 6.70202E-02

FAST encountered an error at simulation time 0.26 of 20 seconds.
Simulation error level: FATAL ERROR

Aborting FAST.

Right now I am using a simple quadratic function to define my sweep with a maximum sweep of 1 m at the tip. I have already read [url]pre-bended & sweep blade simulation with BeamDyn &aerodyn 15] and made sure that I have no kinks in my sweep definition. I attached my aeroDyn blade and beamDyn file to this post. The configuration with just prebent works fine, however the sweep configuration is not working. I am testing by using Test26.fst from the CertTest folder.
FAST version: v8.15.00a-bjj (64bit)
OS: Windows 7 64 bit

Does anyone have similar problems? Or maybe someone has a working setup with swept blades. I would be very happy to have a look at a working setup.
Thank you for your help
Jan Winstroth (3.21 KB) (3.31 KB)

Dear Jan,

I took your files with presweep and was able to reproduce your problem using FAST v8.15 compiled in single precision. However, using the double precision version solves the problem. We typically recommend using the double precision version of FAST when running models with BeamDyn due to numerical sensitivities in BeamDyn that we are still trying to figure out.

FYI ā€“ I was also able to bypass the problem by using a larger induction tolerance (IndToler) in AeroDyn, but this is not generally recommend.

Best regards,

Dear Jason,

thank you for your reply. I am using the compiled version from your website in 64 bit for Windows. I was not able to find on your website whether this version already uses double precision or not. If not I guess I have to compile it myself. Wish me luck :slight_smile:.

THX for the help

Dear Jan,

Actually, in the FAST archive we supply both the single- and double-precision versions for both the 32-bit and 64-bit executables. The double-precision versions have names ending in ā€œdā€ e.g. FAST_x64d.exe.

Best regards,

Dear Jason,

now everything is working fine.

Thank you again for your help