Reply To: How to Analyze Motion Response of Floating Structure With Coupled (2 DOF)?

[Shuangxing Du]

Both Hydrodynamic Diffraction and Hydrodynamic Reponse solve the coupled motions simutantaneously.

In Hydrodynamic Diffraction, the structure mass matrix, hydrostatic stiffness matrix, added mass matrix and hydrodynamic dmaping for a single structure are of 6x6 matrix form, the off-diagonal elements may not be zero, so that the motions, such as heave and pitch, are couplied.  If several structures (n structures for example) are in a hydrodynamic interaction group, the added mass matrix and hydrodynamic dmaping matrix are of 6nx6n matrix form, all the rigid motions of all the structures in this group will be couplied.  The above figure shows the RAOs of the heave and pitch motions, these motions are normally coupled through the motion equations in the frequency domain.

In the Hydrodynamic  Response analysis, the matrices of the added mass/hydrodynamic damping for a hydrodynamic interaction group of n structures are of 6nx6n matrix form, together with the moorings and joints defined between structures,  all the motions of the structures in the model may be coupled.