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Unstable results for cx100 case

Posted: Tue Apr 28, 2020 2:33 am
by Kun.Yang
I am doing a simulation with cx100 blade. However, I tried to modify the case from NREL 5MW wind turbine to Micon 65/13M wind turbine (with cx100 blade) by using limited information from webpages. Finally I got my current case. As I mainly focus on the blade, I close all the DOF except FlapDOF1, FlapDOF2, and EdgeDOF. Then, I got a periodical deflection for blade, which is getting back and forth from -0.15 to 0.15, as shown below:
IPDefl1 .png
IPDefl1 .png (73.79 KiB) Viewed 1019 times

The power is also a fixed number for the whole period.
My worries are about:
1. I am wondering how can I get a stable results like in the 5MW example. I want to get the curve of power with rises at the beginning and getting stable in the end. Should I release more DOF?
2. If so, does anyone have an example for cx100? I can only find the examples for 5MW wind turbine. The information of Micon 65/13M wind turbine is really limited.
(BTW, after searching online, I got to know that the company/NEG Micon was merged with another Danish wind turbine manufacturer, Vestas. But in Vestas, there is nothing about Micon 65/13M either. :cry: It seems that the Sandia laboratory and NREL used to do some experiment on cx100, so I turned to here. :D )

I hope my worries will not violent the rules here. Sorry for bothering.

Many thanks for any help!

Re: Unstable results for cx100 case

Posted: Tue Apr 28, 2020 10:37 am
by Jason.Jonkman
Dear Kun,

I'm not aware of a FAST model that uses the CX100 blades, but you may want to reach out to someone from the Wind Program at Sandia National Laboratories about that. If you are building one of scratch, I would probably start with a FAST model that is bit closer to the turbine you want, e.g., the AWT-27CR2 or the AOC-15/15, which have similar rotor diameters.

Regarding your plot, I'm not too surprised to see a strong oscillation in the in-plane blade deflection; gravity loading tends to cause cyclic oscillations in plane like these.

I'm not really sure I understand your question about the "curve of power". When you disable the generator degree of freedom (GenDOF), then the generator will spin at a constant speed regardless of the loads applied, which--depending on how you've modeled the generator--will likely result in constant generator power output. In this case, it likely makes more sense to output the mechanical power rather than the electrical power (e.g., output RotPwr from ElastoDyn), which is derived from the applied loads.

Best regards,

Re: Unstable results for cx100 case

Posted: Wed Apr 29, 2020 1:46 am
by Kun.Yang
Dear Jason,

Thank you so much for your reply. It really helps! :)

I will try the similar scale of FAST model and also try to enable the GenDOF.

Best Regards,