*DAMPMOTION,NAME=STRU,LINEAR

*DAMPMOTION,NAME=STRU,QUADRATIC

Data format:

Up to 21 lines with 3 parameters each, as follows:

I J VAL(I,J)
...

Status:

Optional.

Purpose:

To define a damping matrix for a structure defined by hydrodynamic database.

Restriction:

The structure named STRU must have been previously defined through the *FPFDX keyword.

Details :

Parameter	Description
STRU	Name of the mechanical structure in the hydrodynamic database (HDB file) to which damping shall be assigned. The name must comprise 8 characters maximum without any blank space.
LINEAR/QUADRATIC	LINEAR: a linear damping matrix is taken into account (applied on the structural velocity V) or QUADRATIC : a quadratic damping matrix is used (generating a damping force on \|V\|V)
OPT=SYM	Option for the quadratic damping matrix. The damping force is applied based on the structure motion as \|V\|V where V is the structure velocity in the direction corresponding to the colum of the matrix. With this option, the norm for column 1 and 2 (translational degrees of freedom) uses the component 1 and 2 of the velocity; similarly for 4 and 5 (rotational degrees of freedom) where component 4 and 5 are used. For VAL(4,4), the force will then be F4 = - VAL(4,4) x sqrt(V4^2+V52) x V4 instead of F4 = - VAL(4,4) x \|V4\| x V4
I	Damping matrix row identification number (must be an integer between 1 and 6).
J	Damping matrix column identification number (must be an integer between 1 and 6).
VAL(I,J)	Damping coefficient I,J of the damping matrix.

Note

The matrix must be symmetrical, therefore for any (I,J) in (1..6,1..6), VAL(I,J)=VAL(J,I).

The value is applied for the low frequency motion if LFOPTION is present and to the wave frequency motion if WFOPTION is present.

Example:

*DAMPMOTION, NAME=FPSO,LINEAR
3 3 1.E7
4 4 1.6 E9