ESyS-Particle

question about damping parameter setup

Asked by KUWABARA Keigo

could you tell me what is difference of Lindampingprms(Rotdampingprms) and Localdampingprms(RotLocaldampingparams).
I read ESyS-particle tutorial. Does Lindampingprms set the resistance of particle in proportion to its velosity such as fluid resistance (Air resistance in tutorial).

Are there parameter to damp just in inter-particle force in rotational particle? In some DEM models, there are spring -dashpot model. I am looking for such model in ESyS-Particle.
Can I achive this using Localdampingprms?

Thank you,
Keigo

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Dion Weatherley
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Best Dion Weatherley (d-weatherley) said : 		#1

Hi Keigo,

Yes, LinDampingPrms applies a damping force that is proportional to the linear velocity of individual particles. RotDampingPrms works similarly, with a force proportional to the angular velocity of particles. These are somewhat similar to air/fluid resistance but the latter generally is not simply proportional to velocity.

LocalDampingPrms (RotLocalDampingPrms) applies a damping force that is proportional to the linear (angular) acceleration of individual particles. LocalDamping is a form of numerical penalty factor that reduces the acceleration of particles, in a similar manner to some quasi-static time integration schemes.

Current versions of ESyS-Particle include SpringDashpotFrictionPrms however this is only for non-rotational particles at the present time. Here is an example for how to use it:

   sim.createInteractionGroup (
      SpringDashpotFrictionPrms (
         name = "pp_friction",
         youngsModulus = 1.0e5,
         poissonsRatio = 0.25,
         restitution = 0.8,
         dynamicMu = 0.6
      )
   )

The restitution parameter governs the level of damping. It is a coefficient of restitution so it determines the ratio between initial kinetic energy and final kinetic energy of colliding particles.

I hope this helps. Have fun!

Cheers,

Dion

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KUWABARA Keigo (kei9713) said : 		#2
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KUWABARA Keigo (kei9713) said : 		#3

Thanks Dion Weatherley, that solved my question.