AeroDyn incongruence?

Dear all,
I would know if RELM values in the AeroDyn input file to FAST must be referred to blade root or hub center (=rotor center). The aerodyn user guide ver 12.50 (but from aerodyn12.58 package) tells on page 12 that RELM is measured from the blade root, while on page 13 in fig 6.1 blade root is referred as hinge or hub center.

The correct answer seems to be hub center because otherwise aerodyn/FAST complains about that… but it’s definitely not clear in the manual.

Thanks for the time you would take to answer my question.


Dear Ste,

When AeroDyn is used by FAST, RELM is defined relative to the rotor (hub) center for both 2- and 3-bladed rotors. We’ve tried to make this clear in the FAST User’s Guide (which refers to RELM as RNodes).

When AeroDyn is used by YawDyn, RELM is defined relative to the teeter hinge (rotor/hub center) for 2-bladed rotors and relative to the blade root hinge for 3-bladed rotors. The AeroDyn User’s Guide heavily emphasizes how AeroDyn is used by YawDyn, hence the confusion.

We are phasing out our support of YawDyn, as should be clear by the latest release of AeroDyn–AeroDyn v13.00.00a-bjj. As we overhaul AeroDyn, we will rewrite the AeroDyn User’s Guide to make the definitions more clear.

I hope that clarifies things.

Best regards,

Perfectly clear.Thanks