Hydrodynamic Coupling
This option enables the user to include hydrodynamic interaction effects between an arbitrary number of bodies. These effects may be significant when the distance between the floating bodies is small.
Two groups of data are considered to enable this functionality:

Coupled added mass (at infinite frequency)

Coupled retardation function
Other load terms affected by hydrodynamic interaction are specified together with body forces (section A2).
The input specification makes use of the symmetric properties:

Coupled added mass: \(\mathrm {(\boldsymbol{A}_\infty)_{i,j}=(\boldsymbol{A}_\infty)_{j,i}^T}\)

Retardation function: \(\mathrm {\boldsymbol{h}(t\tau)_{i,j}=\boldsymbol{h}(t\tau)_{j,i}^T}\)
where the indices i and j refers to body i and body j and superscript T denoted matrix transpose.
Hydrodynamic coupling between several bodies has to be specified as coupling between pairs of bodies.