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Substructure Elements – Buoyancy diameter for rectangular element
For the rectangular elements (SUBELEMENTS_RECT), it is mentioned in the documentation that the diameter (DIA_[m], col 21) is used only for axial forces. But it seems, it is also used to define the buoyancy area (m2) as pi*D^2/4.
Documentation: “The diameter is in this case only used as a hydrodynamic equivalent diameter for the calculation of Morison forces at the end faces of a member (if a HYDROJOINTCOEFF is defined for one of the members end nodes).”
Can you confirm this information?
If it is correct, do you intend to modify the buoyancy area calculation in the future as (XDIM x YDIM)?
Thank for your help and support,
Marie-Laure
Hi Marie-Laure,
using the correct cross-sectional area (y-dim × x-dim) is indeed the intended behavior.
What you’ve observed is a bug that occurs when a rectangular member is fully submerged and the advanced buoyancy feature is activated. In this scenario, the discretization for advanced buoyancy is skipped since the member is fully submerged, and the buoyancy for the fully submerged member is returned as a shortcut. Unfortunately, within this function, the diameter is mistakenly used for rectangular members as well.
You can work around this issue by deactivating the advanced buoyancy feature (remove the ADVANCEDBUOYANCY keyword). Also, for the next release this has been fixed.
Thanks for bringing this up!
BR,
David
