NWTC

Hi Jason,

thank you for the quick answer. You're right, the only output from BModes to FAST would be the mode shapes, so it doesn't really matter what frequency BModes calculates, at least not in this case. I haven't thought about this when asking my question.

Best regards,
Paul

I suggest the following values in BModes when deriving blade mode shapes for FAST: str_tw = 0 (to uncouple the derived flapwise and edgewise modes, which are then coupled through the structural pretwist specified in FAST) tw_iner = 0 flp_iner = very small number (you can't specify exactly zero for ...

Dear Paul, You could select the stiffness-proportional damping in BeamDyn based on a damping ratio (zeta) and natural frequency (f, in Hz) of a given mode using the standard relationship mu = zeta/(pi*f), with the understanding that stiffness-proportional damping produce damping ratios that scale l...

Dear Jason, I have noticed that you recommend a setting of mu = 0.01 as reasonable here, whilst for the NREL5MW reference blades mu = 0.001 is preset. I lack a good feeling for the physical meaning as well as the values of these damping coefficients, as they differ from typical modal damping or Rayl...

Dear Jason, I have just found this topic and wanted to add some remarks regarding my findings. When drastically decreasing the simulation time step to 1e-5s I am able to simulate the model using trapezoidal quadrature and an element order of 8, which I found to be sufficient for convergence regardin...

Dear Jason,

thank you for your help. I will try to implement the point masses as you suggested and look for the topic regarding white noise excitation of the turbine in order to determine the eigen frequencies.

Best regards
Paul

Hello, I have browsed the forum for quite a while but couldn't find a method how to add point masses to the BeamDyn rotor blades (to account for e.g. measurement devices or bolts). Is there any possibility to do so? If not, what would be a suitable procedure to include something similar to point mas...

Dear Jason,

I will focus on the points you mentioned, although I have verified most of the points you adressed already. However, I will tell you if I have gained some new findings.

Regards
Paul

Dear Jason, thank you for having a look at my model. I wonder what exactly you mean with "this is related to how the BeamDyn model has been set-up". Is there another way to set up the model? E.g. should I use more (or less) key points or cross sectional matrices or what do you mean? In thi...

Hello Vahid,

you should probably be more pecise. What would you like to validate? Your model setup, your simulation results, ...?

Dear Jason,

I will send you a message with my FAST model. I have tried to change the BlSwpAC value of node 21 slightly in order so reduce the curvature, but this did not help.

Thanks again for your help,
regards
Paul

Dear Jason, thank you for you quick reply. I would very much appreciate if you could have a look at my input files but I would rather not make it publicly available in this forum. Can I send you an email with my model instead? Regarding you comments: ⋅ Using trapezoidal quadrature it seems...

As I was not able to attach the graph of the initial_twist angle to my last post I will post it here: BeamDyn initial_twist initial_twist.jpg If I understand the BeamDyn manual correctly this initial_twist is the angle of the local principal axes in the sectional coordinate system. The strange angle...

Hello Jason, I still have some problems with the mapping of BeamDyn and AeroDyn. Originally my BeamDyn reference axis was not smooth, but I fixed this and now this shouldn't be an issue anymore. However, I still get various BeamDyn error messages depending on the BeamDyn settings. E.g. for Trapezoid...

I have just found that this errors seems to be related to the AeroDyn BlSpn, BlCrvAC and BlSwpAC values. I am currently using 28 keypoints for the BeamDyn blade reference axis (kp_xr, kp_yr, kp_zr) and 28 stations for AeroDyn as well. If I set the AeroDyn and BeamDyn values to BlSpn = kp_zr, BlCrvAC...