/DAMP/VREL
Block Format Keyword Used to define the Rayleigh mass damping relative to the average velocity of the set of nodes or the motion of the local frame.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/DAMP/VREL/damp_ID | |||||||||
damp_title | |||||||||
CDAMP_Mx | CDAMP2_Mx | grnd_ID | skew_ID | Tstart | Tstop | ||||
Freq | Rby_ID | Func_ID | Xscale | ||||||
CDAMP_My | CDAMP2_My | ||||||||
CDAMP_Mz | CDAMP2_Mz |
Definition
Field | Contents | SI Unit Example |
---|---|---|
damp_ID | Damping
identifier. (Integer, maximum 10 digits) |
|
damp_title | Damping
title. (Character, maximum 100 characters) |
|
CDAMP_Mx | Mass damping coefficient
used for translational direction X. (Real) |
|
CDAMP2_Mx | Mass quadratic damping coefficient used for translational
direction X. (Real) |
|
grnd_ID | Node group
identifier. (Integer) |
|
skew_ID | Skew
identifier. (Integer) |
|
Tstart | Start
time. (Real) |
|
Tstop | Stop time. Default = 1020 (Real) |
|
Freq | Damping frequency. 1 (Real) |
|
Rby_ID | Rigid body identifier. (Integer) |
|
Func_ID | Function identifier
defining damping coefficient scaling factor as a function of
time. (Integer) |
|
Xscale | Abscissa scaling factor
for function Func_ID. (Real) |
|
CDAMP_My | Mass damping coefficient
used for translational direction Y. Default = CDAMP_Mx (Real) |
|
CDAMP_Mz | Mass damping coefficient
used for translational direction Z. Default = CDAMP_Mz (Real) |
|
CDAMP2_My | Mass quadratic damping coefficient used for translational
direction Y. Default = CDAMP2_Mx (Real) |
|
CDAMP2_Mz | Mass quadratic damping coefficient used for translational
direction Z. Default = CDAMP2_Mx (Real) |
Comments
- Rayleigh damping computation
is:Where,
- Viscosity matrix
- Mass matrix
- Nodal viscosity with the direction
- Nodal mass
- If Freq = 0:
- If Freq ≠ 0:
- The damping in the direction
is applied to the node
belonging to a node group (grnd_ID) as follows:
Where, is the relative velocity.
If damping is relative to the motion of a rigid body, force is also applied on the rigid body to keep the global momentum.
- The damping is computed according to the average velocity of the node set (if Rby_ID = 0) or relative to the motion of a rigid body (Rby_ID ≠ 0).
- If skew_ID is defined, the direction x, y and z are the local coordinate system directions.
- It is possible to define multiple
/DAMP or /DAMP/VREL keywords in the
same input file.
Damping is accumulated. It is not recommended to set the same node in different damping cards.