*WDD, NAME= STRUCTURE_NAME

Data format:

A single line with two values IVEL IOP

Status :

Optional

Purpose :

To take into account wave drift damping on a floater

Restriction :

A floater STRUCTURE_NAME must have been previously defined. The wave drift damping is taken into account only if low frequency forces are taken into account in the simulation

Details :

Parameter	Description
IVEL	Option on the velocity to be taken into account for the calculation of the wave damping =1 : Current velocity Floater low frequency velocity =2 : - Floater low frequency velocity =3 : Current velocity
IOP	Option to compute the wave drift damping =0 : The correction on the low frequency force is performed thru a first order matrix multiplied by the velocity (at each wave frequency) =1 : The correction is performed thru a shift (frequency and direction) and a multiplication of the force (drift force or QTF) at wave frequency

Note

The wave drift damping requires that the hydrodynamic database linked to the floater provided the drift forces or the full QTFs forces. The Aranha formulation is used and only the surge and sway forces are modified.
For IOP=0, the correction is considered to be a the first order correction in A Taylor expansion of the force as a function of current velocity. A 2x2 matrix is computed function of the frequency to provide the modification of the low frequency force due to current velocity
For IOP=1: the correction is performed by shifting and multiplying the force withour current based on Aranhas formulation.
Note that if the Newmans approximation is used, the correction is based on infinite depth assumption, while if full QTFs are used, the finite depth correction is used.