Learning Forum

[s.m.mousavi]

We want to model the fluid-structure interaction of a floating offshore platform with the nonlinear RANS VOF model implemented in Ansys Fluent, including a user-defined nonlinear response of the mooring lines, whose variables possibly include the velocity of the fluid interaction with the mooring line. Is it possible to do this using user-defined functions (UDFs)? Can you support us in developing such UDFs?

[Rob]

You should be able to relate the 6DOF force to position, and then link position to the line effects. Assuming that's the case then you will need UDFs. Much of what you need will be covered in the UDF manual, additional material may be available in Learning and the Ansys Learning Hub. 

[s.m.mousavi]

Thank you for the reply message. Can you please clarify your answer, especially what you mean by saying "You should be able to relate the 6DOF force to position, and then link position to the line effects"? Which position? Are you talking about the floating platform or the mooring lines?

[Rob]

The platform, so you know where that is, and can then use terms to work out the resistance force to further movement, less the force pulling the platform back to the "centre" position. 

[s.m.mousavi]

Ok we get your point now, thanks for the clarification. So we want to know if it would be possible to include the velocity field of the domain as a variable in the UDF, to define a distributed load acting on the mooring?

[Rob]

It will be, yes. There's a list of macros in the manual, just be aware that depending on the models the multiphase solver may need additional information regarding phase domain.