Dear @TianYuan.Wang,
Iām not sure I understand your question, but WAMIT computes the potential-flow solution at user-specified reference points (and orientation), which can be, but need not be, the COG of the floater.
Best regards,
Actually I am confused about the 2-nd excitation calculation in OpenFAST.
As mentioned in 4.10.4. Modeling Considerations ā OpenFAST v4.0.2 documentation
The reference point of 2-nd excitation should be the COG of the FOWT. But in OpenFAST (WAMIT2.f90), the 2-nd loads are not further transformed to (PtfmRefxt, PtfmRefyt, PtfmRefzt, PtfmRefztRot)? Or in other words, the effects of the 2-nd loads are always on the COG of the FOWT? For the load transfers from HydroDyn to ElastoDyn, how are the 2-nd loads treated? From (PtfmRefxt, PtfmRefyt, PtfmRefzt, PtfmRefztRot) to PRP (ElastoDyn), or from the COG of the FOWT to PRP (ElastoDyn)
Or maybe (and I think this is more likely), the reference point are treated in WAMIT based on XBODY and XCG
Set XBODY to be the same as PRP, and XCG is the COG of the total system
I am confused about this and look forward to your help.
Best regards,
Tianyuan
Dear @TianYuan.Wang,
You can specify the reference point in WAMIT anywhere you want, including (0,0,0), the COG, or some other point. You should use the same reference point in HydroDyn. In HydroDyn, the reference point for the potential-flow solution is specified via PtfmRefxt, PtfmRefyt, PtfmRefzt, PtfmRefztRot.
Best regards,
Okey, I think you clear my confunsion.
Thank you very much