"T the theoretical stability value "
I was wondering if such values exists (I mean, can be theoretically
derived) for any cases (more than two particles along one axis
especially) ? The (your ?) paragraph you quoted Bruno made me consider
the question...
I just realized that the idea is to consider the discrete numerical model with
a vector X = ( x(body1),y(body1),z(body1),x(body2),y(body2),z(body2),.... ),
and write that our DEM computations leads to write
X(t+dt) = X(t) * f(dt) (1)
With f(t) determined by the fact that the second derivative of X, d²X/dt²
is given by a linear system M d²X/dt² + K X = 0, with M and K the "generalized
mass and stiffness matrices".
Then you end up saying that equation (1) is stable for dt values given by
the classical relation.
Did I understand well ? If yes, I have still few questions :
* does this not depend on the integration scheme which is used ? Depending on
how we compute X(t+dt) from X(t) and d²X/dt², we do not end up with same f(dt)
in equation (1), isn't it ? Then, different values of critical values of dt ?
Or not ?
* the consideration of a linear system M d²X/dt² + KX = 0 assumes no
boundary conditions and no gravity, isn't it ?
* in any case, there should be a typo at last line of
https://www.yade-dem.org/doc/formulation.html#general-mass-spring-system : m /
k does not have the same unit as eigenvalue of M-1 * K
(it would be difficult for me to perform myself the correction)
--
You received this bug notification because you are a member of Yade
developers, which is the registrant for Yade.
https://bugs.launchpad.net/bugs/897237
Title:
bug in neverErase?!
Status in Yet Another Dynamic Engine:
New
Bug description:
If I set neverErase=True Yade crashes with following output:
O.run(3000,True)
RuntimeError: std::exception
and also:
Traceback (most recent call last):
File "/home/me/YADE/YADE2970/lib/yade-bzr2970/py/yade/qt/__init__.py", line
192, in refreshEvent
15:01:13
self.refreshValues()
15:01:30
File "/home/me/YADE/YADE2970/lib/yade-bzr2970/py/yade/qt/__init__.py", line
265, in refreshValues
15:01:34
s=int(t); ms=int(t*1000)%1000; us=int(t*1000000)%1000;
ns=int(t*1000000000)%1000
ValueError: cannot convert float NaN to integer
You can reproduce the bug with the attached script (similar to the one i
submitted with version 2960).
First try to set Law2_ScGeom_MindlinPhys_Mindlin(neverErase=False), this will
work.
Then set neverErase=True and yade crashes.
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https://bugs.launchpad.net/yade/+bug/897237/+subscriptions
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