Question #699605 on Yade changed:
https://answers.launchpad.net/yade/+question/699605
Status: Answered => Open
Fedor is still having a problem:
Thank you very much , but I thought that orthogonal packing ( max porosity)
would have turned into hexagonal packing ( min porosity) during compression and
the porosity would decrease. But now I realized that change of porosity occurs
thank to intersection (overlapping) particles. Does my suggestion make sense?
But in the real soil porosity changes due to particles compaction not
intersection.
But again when I started working with initial script I obtained good relation
pressure/porosity but when I added E , I was confused.
Sent from my iPhone
> On 24 Nov 2021, at 01:41, Jan Stránský <[email protected]>
> wrote:
>
> Your question #699605 on Yade changed:
> https://answers.launchpad.net/yade/+question/699605
>
> Status: Open => Answered
>
> Jan Stránský proposed the following answer:
>> porrr=utils.voxelPorosity(200,(0.75,0.75,0.75),(1.25,1.25,1.25))
>
> The problem here is voxelPorosity and its parameters.
> resolution=200 might be too little, you can try higher values.
>
> More importantly, you are using some random region for evaluation, porosity
> computed there has (or at least may have) no relation to the true total
> porosity. Randomly omitting / adding some border parts of spheres influence
> significantly the result.
> You can play with shifting the region.
>
> If I use an analytical formula
> ###
> def porosity():
> volTot = O.cell.volume
> r = 0.09
> volSphs = len(O.bodies) * 4/3. * pi * r**3
> ds = [2*r - i.geom.penetrationDepth for i in O.interactions]
> # https://mathworld.wolfram.com/Sphere-SphereIntersection.html
> volContactss = [1/12.*pi*(4*r+d)*(2*r-d)**2 for d in ds]
> volContacts = sum(volContactss)
> volSolid = volSphs - volContacts
> volVoid = volTot - volSolid
> return volVoid / volTot
> ###
> I get consistent results:
> 0.47577 (isotropic pressure -1e5)
> 0.47326 (isotropic pressure -5e5)
> 0.47202 (isotropic pressure -7e5)
>
> Cheers
> Jan
>
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