LSMGenGeo: non-uniform particle density when packing cylinders

[Dion Weatherley]

When using LSMGenGeo to pack a cylinder with particles, it would appear that LSMGenGeo has a bias towards inserting larger particles near the top of the cylinder. I have noticed evidence for this in numerous UCS tests where the crown of the cylinder shows a greater propensity to fragment than the base of the cylinder (even when both ends are loaded at the same rate).

I've attached a script for creating a cylinder packing and a couple snapshots that clearly shows the bias towards more larger particles near the crown of the cylinder. The bias is most easily observed if the range of particle sizes is relatively small (e.g. 0.4 to 1.0 or 0.5 to 1.0) but the bias still exists for broader ranges of particle sizes (0.2 to 1.0).

Since this packing bias impacts upon the results of UCS simulations, I'm setting the importance of this bug to High.

[Dion Weatherley (d-weatherley)]

The packing bias described in this bug has been fixed in revisions of LSMGenGeo later than rev. 1232. I have attached a snapshot showing a packing generated by rev. 1269 showing no evidence of the packing bias.

[Jessica (jescarish)]

Hello!!!

I find the script very useful in packing unbonded particles in cylinder. But I have few questions regarding the script.
I wanted to know what are these parameter corresponds.

   sampleRadius = 60.0
   sampleHeight = 180.0
       centrePt = Vec3(sampleRadius,0.0,sampleRadius)
       normalV = Vec3(0,1,0)

[Anton Gladky (gladky-anton)]

 sampleRadius = 60.0
sampleHeight = 180.0
corresponding radius and height of the sample.

centrePt = Vec3(sampleRadius,0.0,sampleRadius) Central point
normalV = Vec3(0,1,0) Vector, which indicates the direction of your
cylinder

______________________________

Anton Gladkyy

2010/2/9 Jessica <email address hidden>

> Hello!!!
>
> I find the script very useful in packing unbonded particles in cylinder.
> But I have few questions regarding the script.
> I wanted to know what are these parameter corresponds.
>
> sampleRadius = 60.0
> sampleHeight = 180.0
> centrePt = Vec3(sampleRadius,0.0,sampleRadius)
> normalV = Vec3(0,1,0)
>
> --
> LSMGenGeo: non-uniform particle density when packing cylinders
> https://bugs.launchpad.net/bugs/513548
> You received this bug notification because you are subscribed to ESyS-
> Particle.
>
> Status in ESyS-Particle: HPC Discrete Element Modelling Software: Fix
> Committed
>
> Bug description:
> When using LSMGenGeo to pack a cylinder with particles, it would appear
> that LSMGenGeo has a bias towards inserting larger particles near the top of
> the cylinder. I have noticed evidence for this in numerous UCS tests where
> the crown of the cylinder shows a greater propensity to fragment than the
> base of the cylinder (even when both ends are loaded at the same rate).
>
> I've attached a script for creating a cylinder packing and a couple
> snapshots that clearly shows the bias towards more larger particles near the
> crown of the cylinder. The bias is most easily observed if the range of
> particle sizes is relatively small (e.g. 0.4 to 1.0 or 0.5 to 1.0) but the
> bias still exists for broader ranges of particle sizes (0.2 to 1.0).
>
> Since this packing bias impacts upon the results of UCS simulations, I'm
> setting the importance of this bug to High.
>
>
>

[Dion Weatherley (d-weatherley)]

Hi Jessica,

sampleRadius = the radius of the cylinder to pack with particles
sampleHeight = the length of the cylinder
centrePt = a position vector (Vec3) denoting the centre point of the base of the cylinder
normalV = a unit vector (Vec3) pointing in the direction of the axis of the cylinder.

If you wish to pack a cylinder of radius 10mm and length 20mm that sits with the centre of its base at the origin and its axis in the y-direction, you would need to set the parameters as follows:

sampleRadius = 10
sampleHeight = 20
centrePt = Vec3(0,0,0)
normalV = Vec3(0,1,0)

Cheers,

Dion.

[Jessica (jescarish)]

Ok. But sorry Sir Anton, I still have not understand what's the central point means. Let's say I wanted to pack particles in a 180 high with radius 60 cylinder. Then the bottom part of my hopper is (0,0,0) and the top is (0,300,0). Now, I wanted to put my packed particles at (0,45,0) above the bottom part of my Hopper, which means the bottom part of my packer will be place at (0,45,0). How will I position this? That is why I got confused with centerPt and normalV.

Jessica

[Dion Weatherley (d-weatherley)]

Hi Jessica et al,

Please can you post any more questions about the cylinder packer on the following question:
https://answers.launchpad.net/esys-particle/+question/100414

I'd prefer to keep discussions on the Bugs pages focused on issues related to the bugs themselves rather than general questions related to using ESyS-Particle or LSMGenGeo.

Jessica, I've attempted to answer your last question in the link above. Let me know if you are still confused by posting to that question.

Thanks.

Dion.