Questions about 5MW_OC3Mnpl_DLL_WTurb_WavesIrr

Wind & Water Computer-Aided Engineering Software Tools
3

Hey @Jason.Jonkman

Thanks for your reply. Could you please correct me if my understanding is wrong after reading your quoted forum topic.
About the coupling between Elastodyn and subdyn. If I active all 6 DOFs of platform in Elastodyn:

  1. All 6 DOF motion/velocity/acceleration at the reference point of platform defined in Elastodyn will be transferred to Subdyn. However, I am not comfirmed which point in Elastodyn is used to transfer the information. Refenrence point of platform, center point of platform or tower base point?

  2. All 6 DOF force/Moment at the interface point defined in Subdyn will be transferred to Elastodyn.

  3. As Elastodyn only adopts 1st and 2nd flap-wise and edge-wise bending mode shape of tower and no torsional mode shape is considered. These adopted mode shapes have taken into account all the inertia of tower except the yaw inertial of tower. Thus, we have to define yaw inertial of tower in Elastodyn file. And for any models (i.e. OC3, OC4 or any other model), PtfmYIner = yaw inertial of platform+ yaw inertia of tower.

  4. There is no need to keep interface point in Subdyn and reference point of platform in Elastodyn at the same x,y,z coordinates. OpenFAST can consider the position offset and transform the information between Subdyn and Elastodyn.

  5. For PtfmCMzt and PtfmRefzt in Elastodyn, are these two values positive when center point and reference point are below ground (onshore) and MSL (offshore)?

  6. Elastodyn adopts bending mode shapes to simulate blade and tower. Thus, I have noticed that some papers say OpenFAST can not consider the torsion of tower. If we model blade and tower as beam elements. By this way, can tower torsion be considered?

  7. we can also model the tower as beam elements using subdyn. To realize this aim, we need to deacitve all the DOFs of tower in Elastodyn, and set TowerHt = TowerBsHt (the tower geometry is zeroed). And set PtfmRefzt = - TowerHt (locate the platform in ElastoDyn at the top of the tower). Model the tower and other supporting structure or floating platform in Subdyn, and set the top node point of tower as the interface point.

  8. If the tower geometry is zeroed in Elastodyn, will it affect aerodynamic load of tower in Aerodyn15? If my understanding is correct, Aerodyn15 is able to calculate the wind load on tower based on tower nodes defined in Aerodyn15. And the instantaneous positions of tower nodes in Aerodyn15 will be updated based on Elastodyn results through node mapping method. So I am confused when we move tower from Elastodyn to Subdyn, can the wind load on tower be calculated correctly?

Regards,
Ran Tu