Hi there,

Could you kindly provide me with a sample input file for user-defined profiles (TurbSim-TIMESR)?

Kind Regards,

Dear Jordi,

The files, “UsrShear.profiles” and “UsrVkm.profiles” (to be used with “UsrShear.inp” and “UsrVkm.inp”, respectively) in the CertTest of TurbSim v2.00.07a-bjj provide example user-defined profile files.

However, you mention “TIMESR”, which corresponds to a user-specified time history. The file, “UserTimeSeries.inp” provides an example of that.

Best regards,

Dear Jason,

Thank you for your directions.

I have managed to create both *.bts and *.wnd files. My goal is to compare SCADA records with simulations, both FAST and Bladed.

When I run the FAST model with the new *.bts file I get the next mesage:

FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:BEMT_CalcOutput(node 35,blade 3):Compute_UA_AirfoilCoefs:UA_CalcOutput:Mach number exceeds 1.0. Equations cannot be evaluated.
SolveOption2:SrvD_CalcOutput:CalculateTorque:u%HSS_Spd is negative. Simple variable-speed control model is not valid for motoring situations.

FAST encountered an error at simulation time 0.5 of 58.8 seconds.
Simulation error level: FATAL ERROR

Aborting FAST.

Is the simulation aborting because of the first message i.e. ‘Mach number exceeds 1.0’, or because of the second one i.e. ‘HSS_Spd is negative’.
Which is the meaning of ‘Simple variable-speed control model is not valid for motoring situations’.

Any idea of how overcome this issue?

All the Best,


Dear Jordi,

Both of those error messages are associated with fatal errors that will stop the simulation. The message regarding “motoring” means that the simple variable-speed control model is not implemented to support a situation where the generator is spinning backwards i.e. where the generator acts as a motor instead of a generator.

It appears that your model is going numerically unstable for some reason (leading to a reversal of rotor speed and large blade velocities), but I’m not sure what might be causing that. I would search the forum for “numerical instability” in the upper right to see how other FAST users have tracked down and resolved numerical instabilities in the past.

Best regards,

Dear Jason,

Thank you for your kindly support.

I have managed to solve the problem by:

  1. Switching off the Simple variable-speed control.
  2. Reducing the time step.

My blades are extremely flexible, I am not sure if this fact can lead to the numerical instability itself, but most importantly I am using a controller which works, but it is not specifically designed for my machine. Could any of those be the reason for the numerical instabilities?

As I said, I solved the problem. The simulation works with a few of warnings regarding small angles violation. The results match quite well both, the Bladed commissioning results and the SCADA data so I am happy with the simulation.

Any comments at all? Do you think that implementing BeamDyn instead of ElastoDyn could be worth? Or is it more likely that the problem comes from the controller? I am using the DTU_controller.

All the Best,


Dear Jordi,

Extreme blade flexibility will not cause numerical instability, but it may lead to “small angle violation warnings” and a loss of accuracy. If you routine get these warnings, I would recommend modeling the blades with BeamDyn instead of ElastoDyn; BeamDyn was developed to accurately model large blade deflections.

The use of an incorrect controller could cause physical or numerical problems that will result in simulation failure.

Best regards,