Damping Matrices

Damping matrices models damping forces acting on a body. The damping forces are applied in the body-local coordinate system and are caused by body-local velocities.

1. Linear Damping Matrix

For linear damping matrices the force is calculated by

\(\boldsymbol{F} = \boldsymbol{D}_1 \boldsymbol{v} \)

where

  • \( \boldsymbol{D}_ 1\) is the linear damping matrix

2. Quadratic Damping Matrix

For quadratic damping matrices the force is calculated by

\( \boldsymbol{F} = \boldsymbol{D}_2 \boldsymbol{v} | \boldsymbol{v} | \)

where

  • \( \boldsymbol{D}_ 2\) is the quadratic damping matrix

3. Input parameters for linear and quadratic damping matrices

In both cases, the body velocity, \(\boldsymbol{v}\), depends on the choice of motion mode:

  • Default: If the body is of type 6 DOF - separated analysis the low frequency velocity will be used, otherwise the total velocity will be used.

  • Low frequency: The low frequency velocity will be used.

  • Wave frequency: The wave frequency velocity will be used.

  • Total: The total velocity will be used.

For bodies of type 6 DOF - time domain the low frequency motion must be estimated to use either the low or wave frequency velocity.
If the low frequency motion estimation is not used the total motion will be used instead. See Body.