yade-dev team mailing list archive

[Chiara Modenese <c.modenese@xxxxxxxxx>]

Many thanks, Bruno, for this indeed clear explanation. It would be more than
worth to report some of it in Yade documentation ;-) I will think about
closing the bug and will let you know about it.
Cheers! Chiara


On 12 November 2010 19:11, Chareyre <674000@xxxxxxxxxxxxxxxxxx> wrote:

>
> > I have two questions, one of which is for Bruno. My first point is that I
> do
> > not understand the origin of the convective term (see the discussion we
> had
> > in the thread I mentioned before) that you actually introduced
> In 1D :
> Say we have period size =1.
> 1) If point is at position x=1, it will be assigned a mean-field
> velocity v_p= 1*velGrad (Cundall's equation).
> 2) If it is at position 0, it will get the velocity v_p=0.
> 3) Remember we don't modify v_p if velGrad is not modified.
>
> So, let's see what can happen in an extreme case : in one step, particle
> goes from x=1 to x=0 (on its own, not because of the period deformation) .
> Without the convective term, the particle will still have v_p=1*velGrad,
> which is not consistent. It should be v_p=0.
> With the convective term, it will give v_p=0.
> Actually, this correction is accounting for the motion of particles in a
> v_p field that is constant in time but not constant in space.
> In most cases, particles will have "free motion" way smaller than the
> period, and the effect will be negigeable.
>
> For me, homo=3 is emulating Cundall's way. Why did I implement it that
> way? Precisely because I didn't want to solve this bug you just opened.
> It was simpler to work on velocities, especially because Yade is not
> working in reduced periodic coordinates (positions always between 0 and
> 1). Instead, it uses absolute coordinates and never distinguises
> absolute velocities and mean-field velocity v_p.
>
> Bruno
>
> --
> homoDeform=1 does not handle the periodic case correctly.
> https://bugs.launchpad.net/bugs/674000
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in Yet Another Dynamic Engine: New
>
> Bug description:
> Currently, in the periodic case, if homoDeform=1 (alias Cundall way) we do
> not adjust the values of the relative velocities as according to the
> velocity gradient. This should be done, since, in such a case, we only
> update particle positions and not particle velocities.
>
> To unsubscribe from this bug, go to:
> https://bugs.launchpad.net/yade/+bug/674000/+subscribe
>

-- 
homoDeform=1 does not handle the periodic case correctly.
https://bugs.launchpad.net/bugs/674000
You received this bug notification because you are a member of Yade
developers, which is subscribed to Yade.

Status in Yet Another Dynamic Engine: New

Bug description:
Currently, in the periodic case, if homoDeform=1 (alias Cundall way) we do not adjust the values of the relative velocities as according to the velocity gradient. This should be done, since, in such a case, we only update particle positions and not particle velocities.