Coordinate that is the standard for calculating Moordyn module outputs (CON#FX, CON#FY, CON#FZ..)

Dear all,

Hello. I am checking the tension of a 10mw FOWT’s mooring system through Moordyn. I am using the functionality of CON#T, CON#FX, CON#FY, and CON#FZ to check the mooring tensions, as there are several segments that distinguish the mooring lines.

One thing I am curious about is whether the results from CON#… that appear as Moordyn output are calculated based on Global coordinates or if they are based on the Platform’s reference coordinates.

I have reviewed many books and materials related to Moordyn, but I have not found a clear answer, so I am asking on the forum. I would sincerely appreciate it if you could provide an answer.

Thank you.

Dear all,

Hello. The question above pertains to calculating the angle of the catenary line at the fairlead, using the load component (CON#FX, CON#FY, CON#FZ) on the fairlead.

The calculation coordinates of Tension are crucial for angle calculations.

Based on the Moordyn reference literature, it appears that calculating the tension in the catenary with respect to Global coordinates is the approach being taken. I would like to confirm if this understanding is correct.

I would greatly appreciate a brief response to the question.

Best regards,

In MoorDyn, forces and moments in x/y/z are always aligned with the global reference frame. All position x/y/z outputs are in global coordinates (typically z=0 is at the waterline, etc.).

We’re working on some improved documentation and will make sure this is clearly stated.
Thanks for the question,

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Dear Matthew.Hall

Thank you for kindly providing answers to my questions about the MoorDyn coordinate system.

Your response has been incredibly helpful to me. I appreciate it.

Best regards,