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[Jan Stránský <question703901@xxxxxxxxxxxxxxxxxxxxx>]

Question #703901 on Yade changed:
https://answers.launchpad.net/yade/+question/703901

Jan Stránský proposed the following answer:
Instant replay:

please provide more information, e.g. what particle size distribution you use, what materials and laws, ...
Basically a MWE [2].

utils.PWaveTimeStep() is simply min(radius/sqrt(young/density))
GlobalStiffnessTimeStepper [3] computes actual stiffness, includes viscosity if needed etc. (basically is much more sophisticated) so a different result is expected.
You can e.g. try to put two spheres and then four spheres at almost same position, the GlobalStiffnessTimeStepper is different, whereas the PWaveTimeStep is constant:
###
# GlobalStiffnessTimeStepper is included in the default engines
xs = [0, 1]
#xs = [0, 1, 0.1, 1.1] # un-comment this line for the second run
O.bodies.append([sphere((x,0,0),1) for x in xs])
O.step()
print(O.dt,PWaveTimeStep())
###

Cheers
Jan

[2] https://www.yade-dem.org/wiki/Howtoask
[3] https://gitlab.com/yade-dev/trunk/-/blob/master/pkg/dem/GlobalStiffnessTimeStepper.cpp

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