yade-users team mailing list archive

[kan <nicessgg@xxxxxxxxx>]

Hi, buddies,

I have some questiones.
1. how to get the micro-force from the macro-stress?
As we know,for most of current studies, the concept of stress is used to
describe the stress status. but when we look into the micro level, we have
to convert the macro-stress to descrete force that applied at each particle,
then how to do this convert?

2. what is the calculation process in each time step?
The problem is that, as see the relation ship below,
___\|/____\|/___\|/________
01---02---03---04---05---06...
|   \   |  /  |      |       |      | ...
11---12---13---14---15---16...
|      |      |   /  |   \  |      |...
21---22---23---24---25---26...
...
...
x1---x2---x3---x4---x5---x6...

in which, the number is the ID of a particle,
and "--- " , "/" ,"\" and  "|" between the numbers mean there is a contact
between the particles
"\|/" means force.
assume the 01-02-03-04...is the upper bounday layer, and the force is
applied as shown "\|/".
when the calculation begins, we need to detecte the contact and update the
position of each particles,
now my problem comes:
what is the procedure to calculation and update the particles' information,
you know the force is from up layer, so the first layer ("01-02-03-04...")
should be calculated, then the second layer,and then the third layer.... but
in DEM, the particle is independent to move, so after some time, some
particles in the first layer may move to the second layer and some particles
in second layer may  move to the first layer(other other layer),then how
should I do in order to know which particle should be calculated and updated
first and which should be done later in the same timestep?
For example,
01 has contacting neighbors 02 and 11, in a same timestep, after we have
calculated 01's properties( velocity, position....), we should calculate 02
first, then 03(the neighbor of 02), after the layer of 01-02-03...is done,
then we can step to calculate the 11, which is to say, in a same timestep,
though 02 and 11 are both contacting neighbors of 01, we should calculate
02, and 11 later though 02 and 11 are both affected because of teh movement
of 01. so, how to indentify which particle should be calculated and update
first , and which should be later?
(because it is a dynamic process, so just use the order of  ID  is not  a
way to solve this)

Hope I have described the problem 2 clearly,

Need your help, thanks so much.

Kan

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