Mooring mass matrix

Dear all,

I have a full system mass matrix of OC4 semisubmersible turbine.

Is there any way to find the mass matrix associated with mooring line from this full system matrix ?

Also is there any manual way of finding the mooring line mass matrix ?

Best regards,
Kajal Thakur

Dear @Kajal.Thakur,

Can you clarify your intent? It is common in some situations to assume that a floating offshore wind turbine is rigid, but this would never be a good assumption for a mooring system, which never acts as a rigid body.

Best regards,

Dear @Jason.Jonkman ,

I just want to see the contribution of mooring line mass in whole system mass matrix.

Best regards

Dear @Kajal.Thakur,

MoorDyn does not have the ability to treat the system rigidly, so, I’m not aware of any way for MoorDyn to output its equivalent rigid-body mass matrix.

Perhaps someone more experienced with MoorDyn can correct me.

Best regards,

Hi @Kajal.Thakur, Jason is right there is no way to output the mooring system mass matrix from MoorDyn because it does not exist. Each mooring line is simulated as a lumped mass model, with the dynamics and mass of each lumped mass calculated separately. If you are looking for a linearized mooring model OpenFAST has Map++ available.