Dear Mitesh,
Just a few comments:
- I still see gravity set to 9.81 m/s^2 in your spreadsheet.
- There is a bug in the vertical component of the buoyancy force (BuoyFzi) reported in the HydroDyn summary file; it is incorrectly reported based on the total structure volume rather than the submerged volume. It sounds like we were aware of this bug and offered a fix a couple years ago, but this fix doesn’t seem to have been implemented in the current OpenFAST code base. More information is available in the following topic on the forum: Water ballasting & buoyancy loads - #3 by Romain.Quancard. I’ve now reported this issue in OpenFAST: github.com/OpenFAST/openfast/issues/202. Regardless, I agree with your hand calculation based on the submerged volume.
- The total mass in your spreadsheet doesn’t match your ElastoDyn summary file. It should be 13162804 kg.
- Running your model, it doesn’t appear that MoorDyn even generates a summary file (and I don’t see that you’ve attached one, so I’m not sure how you got your value). I converted your MoorDyn input file to MAP++ and when I ran that, the vertical mooring tension on each fairlead is around 1.6E6 N, so, quite a bit lower than you are reporting.
- The above differences lead to an imbalance in the vertical equilibrium condition. But I’m not sure which term (displaced volume, mass, pretension) should be changed to resolve the problem.
Best regards,