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Computing RAOS with AQWA

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Old   July 24, 2015, 13:24
Default Computing RAOS with AQWA
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Hi everyone,

I'm trying to compute RAOs of a FPSO using Ansys AQWA. But it seems I'm doing something wrong because the RAOs of some degrees of freedom are completely out of range (27 deg/m in roll, while 5 deg/m expected) even if the general allure of the curves are fine (with pic periods corresponding).

I thougth I was doing everything right, step by step :
  1. Selecting hydrodynamic diffraction module
  2. Define geometry, add point mass and generate mesh
  3. Analysis setting : GOON option enabled, calculate full QTF disabled
  4. Selecting wave directions and frequencies
  5. Inserting results "RAO distance/rotation vs frequency"
  6. Run calculation

I'm pretty my geometry and mass/inertia distribution are okay because hydrostatics are fine.

Does anyone know if AQWA's output must be dimensionalized by some factor, or if I forgot any option during calculation, or something else ?

Thank you.
Regards,
Antoine
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Old   July 27, 2015, 10:33
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It seems that I must define an additional damping due to viscosity. After a quick search, I read that the FIDD could suffice, but I didn't really understood how to use it. Please could someone explain it ?
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