gran/hertz/history

When I use gran/hertz/history with friction_damp_flag=1 but coefficientFriction=0 I got torque!=0 (but history=0). Is this bug or not?
ps. It is for liggghts 1.5

Forums:

Bug Reports for CFDEM®coupling, LIGGGHTS®, and ParScale

ckloss | Tue, 02/21/2012 - 13:31

Hi Sergei, following the

Hi Sergei,

following the pair_gran.html doc: friction_damp_flag = 1 if tangential damping is included
This means that tangential damping is applied, leading to no non-zero tangential forces.

Cheers, Christoph

SergeiD | Tue, 02/21/2012 - 14:23

Hi, Christoph Is the

Hi, Christoph
Is the tangential damping force a only viscous force rather than elastic+viscous force?
And if friction is zero then what do mean non-zero tangential force? Is it artifical?
Thanks!

ckloss | Thu, 02/23/2012 - 13:06

>>Is the tangential damping

>>Is the tangential damping force a only viscous force rather than elastic+viscous force?
In the case you describe, yes

>>And if friction is zero then what do mean non-zero tangential force? Is it artifical?
In that case it's just the damping part of the tangential force, as described in the manual

Does that clarify it?

Cheers, Christoph

SergeiD | Fri, 02/24/2012 - 08:08

I mean what if Ft <= mu * Fn,

I mean what if Ft <= mu * Fn, then Ft should be zero if mu is zero, regardless of whether Ft=Felastic+Fviscous or Ft=Fviscous or any other expression. Seems, it is expected behavior. No?

ckloss | Fri, 03/02/2012 - 13:00

In LIGGGHTS only the elastic

In LIGGGHTS only the elastic part of the force is used for the coulomb criterion. I know there are a couple different implementations and debates in literature...

Christoph