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Gravity Command

The Gravity command adds a gravitational force field to an MPM simulation:

Gravity <(accx)>,<(accy)>,<(accxz)>

where (accx), (accy), and (accz) are the accelerations due to gravity (in acceleration units) in the x, y, and z directions, respectively ((accx) (accy) are for R and Z directions in axisymmetric calculations). All three parameters are optional. If any are omitted, the gravitational force field is set to Earth's gravity with down being in the negative y direction (i.e., the default values are (0,-9806.65 mm/sec2,0) in Legacy mode or (0,-9.80665 acceleration units,0) in consistent units mode).

Any of the parameters can alternatively be a user-defined function of x, y, and z (in length units) and t (in alt time units) to give position and/or time dependent body forces. The functions should evaluate to acceleration in acceleration units.

Notes

  1. If no Gravity command is used, the simulations will have no gravitational forces. Thus to have Earth's gravity you need a command, even if it has no parameters.
  2. The Gravity command is only allowed for MPM analyses.