Varying torque applied to the main shaft

Hi Jason,

I recently found this potentially very helpful simulator FAST for my WT fatigue studying. I first want to model the varying torque applied to the main shaft which connects to the gearbox. The varying torque is certainly caused by the aerodynamic load that is instantaneously changing due to the varying wind speed and controls, I think FAST can provide very promising load output results, right? So my question is, what output term I can use appropriately to address varying torque applied on the main shaft, ‘Aero_Torq’ or ‘RotTorq’?

Thank you so much for your help.

Regards,
Fangfang

Dear Fangfang,

I’m really sure I understand your question, but “Aero_Torq” is not actually an output of FAST. My post dated Jun 10, 2010 in the following forum topic explains the difference between RotTorq, which is an output of FAST, and the applied aerodynamic torque (AeroTorq): http://forums.nrel.gov/t/fast-aerodyn-beddoes-stall-mode/258/1.

Our next release of AeroDyn within FAST v8 later this summer will include applied aerodynamic load outputs.

Best regards,

Hi Jason,

Thanks a lot for your quick reply, will look at your suggested post first.

Regards,
Fangfang

Jason,

I have tried to run FAST using the sample model test13, which is distributed in the FAST archive file. Different from test01, there is not RotTorq output values, would appreciate if you can advise me how do I do if I want to generate RotTorq using test13 model?

Regards,
Fangfang

Dear Fangfang,

Simply add “RotTorq” to the list of outputs at the end of the ElastoDyn input file.

Best regards,

Got it, thanks a lot Jason!

Regards,

Hi Jason,

Can I simply modify the input ‘VSContrl’ to be ‘0’ in ‘test13.fst’ , so that the sample 13 can run as a fixed rotation speed WT? of course there are some relevant input parameters need to be changed as well.

Dear Fangfang,

With the generator DOF enabled (GenDOF = True), you should only set VSContrl to 0 when also defining a proper generator model (GenModel). Instead, if you want the rotor to generator to spin at a fixed speed regardless of the torques applied, disable the generator DOF (GenDOF = False).

Best regards,

Thank you so much, Jason, so instructive and quick feedback.

Hello Jason,

There is one more question today :slight_smile:, what can I do if I want to simulate the data over longer than 40s period, there is a aborting notice “FF wind array was exhausted at 43.17 seconds…”?

Dear Fangfang,

The FAST CertTest only provides sample input; the wind files in particularly were purposely made very short to reduce the size of the FAST archive. You should run TurbSim to generate the turbulent wind data that you need for your own use: nwtc.nrel.gov/TurbSim.

Best regards,

OK, will try that. Thanks a lot!

Thanks again Jason, what wonderful responses that help me very efficiently!

Helps me too with my studies! Thanks Jason and Fangfang.Ding! :slight_smile:

u r welcome, Malika.Sharma, good to know it is helpful to the people who might be on the same boat :slight_smile: