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### calculation of hydroForce on a given member

Posted: **Wed Aug 07, 2019 9:27 am**

by **Florence.Haudin**

Good afternoon,

Is it possible to calculate the hydroForce and hydroMoment of a selected member ?

If yes, is there somewhere an example of the .dat configuration file ?

Thanks in advance.

Best regards.

Florence Haudin.

### Re: calculation of hydroForce on a given member

Posted: **Wed Aug 07, 2019 9:48 am**

by **Jason.Jonkman**

Dear Florence,

Are you asking about outputting from HydroDyn the total hydrodynamic applied forces and moments on a specific member of the substructure? This is not a standard output from HydroDyn. Of course, you could output the hydrodynamic applied forces and moments distributed along a member and integrate them to calculate the total loads. The list of available outputs (not requiring a change to the source code) is available in Appendix C of the draft HydroDyn User's Guide and Theory Manual:

https://wind.nrel.gov/nwtc/docs/HydroDyn_Manual.pdf.

Best regards,

### Re: calculation of hydroForce on a given member

Posted: **Wed Aug 07, 2019 11:34 am**

by **Florence.Haudin**

Good evening Jason,

Thanks for your reply.

I indeed was referring to the output of Hydrodyn.

I have read the documentation and seen the available outputs. But from what I understand, the member and joints outputs are forces for the strip theory (Drag, inertia at least). I am interested in using the potential flow theory and have the total force for instance let's say on the main column of a trifloater composed of different cylindrical members.

I am quoting you, you wrote : "you could output the hydrodynamic applied forces and moments distributed along a member and integrate them to calculate the total loads". But I don't see how for the potential flow theory.

Best regards.

Florence.

### Re: calculation of hydroForce on a given member

Posted: **Wed Aug 07, 2019 12:03 pm**

by **Jason.Jonkman**

Hi Florence,

OK, thanks for clarifying. When you referred to a "member", I assumed you were referring to the strip-theory solution of HydroDyn, which is based on joints and members.

For the potential flow solution, it is not currently possible in HydroDyn to extract portions of the load for separate members because HydroDyn only calculates the total integrated load on the single WAMIT "body" solved via potential flow. That said, we are currently working on an upgrade to HydroDyn (among other improvements) that will enable it to solve for the hydrodynamic loads on multiple potential-flow bodies (corresponding to the so-called "N-body" option in WAMIT). While not fully implemented, when complete, this will be significant upgrade in HydroDyn functionality. Stay tuned.

Best regards,