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[Question #679050]: GSTS gives an unstable dt?
New question #679050 on Yade:
I'm Alessandro and I'm a new Yade user. I have to simulate the behaviour of a given set of spheres (radii, material, accelerations are given) inside a cylinder. I use yadedaily, xenial version.
The given set of accelerations translates into amplitudes of the HarmonicMotionEngine up to 7 mm. And here I find my problem: up to 1-2 mm all is ok, no unstability problems. But when I try, for example, with an amplitude of 3.5 mm, the spheres begin to overpass the facets of the cylinder and, as far as I know, it could be an issue linked to instabilities.
Firstly I tried to use a smaller dt, then I read about GSTS and decided to move to that. It wolud be perfect for my purpose: in the first part of the script I need a sort of "gravity deposition" and so a bigger dt would be nice, then the GSTS should assure the right dt in order to avoid instabilities (if I understood correctly).
But using GSTS, even with a very small safety coefficient, the spheres keep overpass the facets. I have to admit that with a lower coefficient the simulation seems to be improved, but the problem is not solved.
So: do you think that's an instability issue? Is the decreasing of the safety coefficient the only way to improve it? And shouldn't GSTS give a pretty good dt even without this very small coefficient?
I've used both CoundallStack (now commented) and ViscElPhys, and my problem is present in both cases.
Here I attach my script:
### MOVIMENTO ARMONICO ALTO BASSO
from yade import pack,utils,plot,ymport,export,qt,timing
## Physical Parameters
en = 0.5
es = 0.5
cyl_r = 12.7
cyl_h = 24.6
sp_p_r = 1.5
fill_size = 11.5
young = 200e9
poisson = 0.305
## Creation Cylinder
## Creation Spheres
if O.iter<15000: return
if kineticEnergy()>18000000: return
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