Gravitational Field

Gravity Commands

MPM simulations can include gravity or any other constant body forces. In scripted files, the command to add gravity is:

Gravity <(gravX)>,<(gravX)>,<(gravX)>

In XML files, gravity is added with the element:

<Gravity>
  <BodyXForce>(gravX)</BodyXForce>
  <BodyYForce>(gravY)</BodyYForce>
  <BodyZForce>(gravZ)</BodyZForce>
</Gravity>

where (gravX), (gravY), and (gravZ) are the accelerations due to gravity in the x, y, and z directions, respectively ((gravX) and (gravY) are for R and Z directions in axisymmetric calculations). In scripted files, the units are m/sec², but in XML files, the units are mm/sec².

In scripted files, all three parameters are optional. If all are omitted, the gravitational force field is set to Earth's gravity with down being in the negative y direction (i.e., it is equivalent to the command Gravity 0,-9.8,0). If (gravX) is included, but (gravY) and/or (gravZ) are omitted, the omitted parameters will be set to zero. In XML files, any omitted forces are set to zero.

Notes

1. If no Gravity command is used, the simulation will have no gravitational forces. Thus to have Earth's gravity you need a Gravity command, even if it has no parameters.