servo walls maintaining a specified confining pressure

Hi Ceguo,

ESyS-Particle provides a subroutine LsmMpi.applyForceToWall(..) that implements a servo wall for assigning a constant force to a given wall. It is quite similar to the LsmMpi.moveWallBy(..) subroutine, used in the WallLoader Runnable in the tutorial on uniaxial compression.

To implement a servo wall, you need to do three things:

1) add a wall to your simulation script e.g.

   sim.createWall(
      name = "servoWall",
      posn = Vec3(0.0,0.0,0.0),
      normal = Vec3(1.0,0.0,0.0)
   )

2) define the type of interactions between that wall and particles in your simulation script e.g.

    wp1=NRotElasticWallPrms(
       name = "servoWallInteraction",
       wallName = "servoWall",
       normalK = 1.0
    )
    sim.createInteractionGroup(wp1)

3) write a runnable containing a run(..) subroutine in which you assign a constant force to the wall via its Interaction Group e.g.

class ServoWallLoading (Runnable):
   def __init__(self, sim=None):
      Runnable.__init__(self)
      self.sim = sim

   def run (self):
      self.sim.applyForceToWall(
         interactionName = "servoWallInteraction",
         force = Vec3(100.0,0.0,0.0)
      )

N.B. applyForceToWall(..) expects the name of a wall's Interaction Group (e.g. servoWallInteraction) not the name of the wall itself.

Of course for a triaxial test you will need to define four walls, four interaction groups and your Runnable will need four calls to LsmMpi.applyForceToWall(...) to implement servo walls for all four sides of the model.

Good luck and have fun!

Cheers,

Dion.