Moment(about z) of tower top under EDC wind case

Hi,

The moment about z axis at the tower top calculated by FAST has a big moment jump during the EDC wind case, whereas the moment calculated by Bladed does not change so much. Could anyone give me some suggestions? The wind changes 90 degrees. The yaw degree of the rotor is disabled.

Thanks
Best regards

Yinping Yang

I can’t answer this specific question (Jason will have to do that), but I can offer some general guidance for doing code comparisons, as I’ve done a few over the years.

Always start as simple as possible. Make the turbine totally rigid and turn off aerodynamics. If a code does not have the ability to switch off aerodynamics, set the air density to zero. One you get all measurements agreeing for that case, add aero, but still keep things rigid. Work up from there by adding DOFs one at a time. It takes a long time to do all that, but it’s the only way to success. If you start with full models, it’s extremely difficult to figure out what is causing a difference.

Dear Yinping Yang,

See my previous post for reasons why FAST may generate nonzero yaw moments: http://forums.nrel.gov/t/shear-force-x-at-the-tower-base/245/1 (Bladed may not treat all these the same).

It is difficult to answer your questions regarding FAST and Bladed comparisons because we do not offer support for Bladed at NREL. May I ask why you’re comparing FAST and Bladed? Have you also contacted GH for support?

In his post, Marshall offered very useful advice for code-to-code comparisons. I suggest you follow his guidance before posting more questions on this forum.

Best regards,