I was reading the OC7 WP2.2 reports and reviewing the model and result files uploaded to Zenodo, and I noticed something strange in the Nastran modal analysis file.
According to the report and Description workbook, the modal analysis was to be run on a free-free model, with the aim of ensuring all participants were on the same baseline before the actual load transfer evaluation.
However, upon inspecting the Nastran model, there are a multitude of MPCs defined.
My suspicions are either of the following:
- The MPCs represent a hull pressure field and were incorrectly exported from ANSYS
- The MPCs represent a glue contact between the different parts of the floater structure (pontoon to columns, pontoon to scantling, column to scantling)
Is either of my suspicions correct?
Hi @Gustavo.Hylander,
Personally, I used the ANSYS mesh instead of the Nastran one during the OC7 Phase II WP2.2.
I remember that Ramboll created a Nastran model from the ANSYS one. Later on, Jon Cerrada from CENER made improvements on that Nastran model. The MPCs were introduced to link the different meshes. This should be also reflected in a MPCADD entry that includes all the MPCs. He also replaced the tower connection with RBE2 elements.
Regarding the question about the pressure field, the original ANSYS model does not contain a pressure field. The hydrostatic pressure had to be included by the different participants.
Keep in mind that during the project, 4 different modal analysis were performed:
LC 3.1: floater only, unconstrained. This should be the OC7_FE_MODEL_v3_modal.bdf model in Zenodo
LC 3.2: floater and wind turbine, unconstrained. This should be the OC7_FE_MODEL_Subs+tower+RNA_modal.bdf model in Zenodo
LC 3.3a: (rigid) floater and wind turbine, in water, with morings
LC 3.3b: (flexible) floater and wind turbine, in water, with morings
I hope this helps!
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This is consistent with my second hypothesis
Thank you for the confirmation, Roger
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