Simulate with complex geometries and complex physics
MassSpringDashpot
movement of a mass-spring-damper system, coupled (by joints) with other %MOVE_rigid% or %MOVE_MassSpringDashpot% items
MOVE($MOVE_index5b$) = ( %MOVE_MassSpringDashpot%, mass, precompressionForce, springConstant, dampingConstant, OPTIONAL: Spring Force, OPTIONAL: Damping Force )
A mass-spring-damper item comprises of exactly TWO instances of an FPM_point . Those two points initially mark the beginning and end location of the spring, and the form connection bonds to other %MOVE_rigid% or %MOVE_MassSpringDashpot% items.
On the other hand, it can have triangles and lines, which are used to compute the hydrodynamical forces on the spring-damper-system, however they are not compulsory.
If optional non-zero spring and damping forces are provided, then the total forces are calculated as follows : \begin{align}
{\bf F_{spring}} = {\bf F_{spring}} + {\bf K} \cdot {\bf dx} \\
{\bf F_{damping}} = {\bf F_{damping}} + {\bf C} \cdot {\bf dv}\end{align}
where, \( {\bf F_{spring}}\) is the total spring force, \( {\bf F_{damping}}\) is the total damping force,
\( {\bf K}\) is the springConstant, \( {\bf C}\) is the dampingConstant.
\( {\bf dx}\) is the change in spring length which can be obtained via the function xCOG(4) or xCOG(5), see xCOG() for more details.
\( {\bf dv}\) is the change in length rate which can be obtained via the function vCOG(4) or vCOG(5), see vCOG() for more details.
begin_alias{}
"MSD" = " ... MOVE$MOVE_MSD$ ... "
end_alias
begin_boundary_elements{}
BND_point &MSD& x1 y1 z1 # most preferebly, these points should link to other BND_point items of other MOVE-statements (%MOVE_rigid%, ... )
BND_point &MSD& x2 y2 z2 # otherwise, the spring-damper-system would hang in the air
end_boundary_elements
MOVE($MOVE_MSD$) = ( %MOVE_MassSpringDashpot%, mass, precompressionForce, springConstant, dampingConstant , OPTIONAL: Spring Force, OPTIONAL: Damping Force )