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[Jérôme Duriez <question692478@xxxxxxxxxxxxxxxxxxxxx>]

Question #692478 on Yade changed:
https://answers.launchpad.net/yade/+question/692478

    Status: Open => Answered

Jérôme Duriez proposed the following answer:
Hi Luc,

No, there is only one way of calculating that (rather arbitrary) maximum
dimensionless suction value [1].

Maximum suction is here the first suction value for which the mean
filling angle between two (liquid-bonded and contacting) particles is
less than 0.7 degrees.

"first" referring to a geometric sequence of suction values, starting
from low suction (and filling angle >> 0.7 degrees), and multiplying
each time by 1.2 [2]

There is a "step" aspect here and I think this explains that non
monotonous variation.

When one is able to high-jump 0.50 m but fails at 1.5 m, it does not
mean that 0.5 m really constitutes his high-jumping maximum level (maybe
the guy could jump 0.9 m but he did not get the opportunity to try).

In terms of liquid bridges, maybe the (r=1.75;uc* = 26389) reached a
mean filling angle = 0.4 degrees, while uc* = 26389/1.2 led to just 0.71
degrees, barely passing the test to multiply uc* by 1.2.

Whereas the situation would be different for r=2, with the last filling
angle reached being equal to 0.69 => no need to increase uc* further,
even though the corresponding liquid bridge is not as tiny as the
previous one.


As for the consequences on the output files, you may see the M(r=2) file missing more capillary bridge configurations than the M(r=1.75) one, in the high suction regime.

(Both files miss capillary configurations anyway since theory says that
a non-zero capillary attractive force exists until infinite suction, and
that's not the case in both files)

Nothing to worry if you do not go in that regime. 
If you go, YADE should output a message saying that no meniscus is found at a contact, which contradicts the above theory.


[1] That "Preliminary C" block at https://gitlab.com/yade-dev/trunk/-/blob/master/examples/capillaryLaplaceYoung/writesCapFile.m#L84
[2] https://gitlab.com/yade-dev/trunk/-/blob/master/examples/capillaryLaplaceYoung/writesCapFile.m#L103

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