[ESPResSo-users] fluid-particle coupling in different LB resolutions

[Iveta Jancigova]

Hello, 

I want to ask about a strange behavior I encountered:

When I put a single particle in the center of a channel 20x10x10 with fluid 
(ext_force on fluid 0.0001 0 0, dens 1, visc 1) and look at the velocities of 
the particle and fluid at the same position, I get the following:
for grid=1:     v_fluid ~ 0.000728167   v_part ~ 0.000723167
for grid=0.5:   v_fluid ~ 0.000737281   v_part ~ 0.00018307
for grid=0.25:  v_fluid ~ 0.000738749   v_part ~ 4.58593E-05
While the fluid velocity is roughly the same, the particle velocity seems to 
decrease ~4 times when the grid size is halved.

I have tried varying the friction parameter (even by orders of magnitude) but 
it only made minimal difference. I suppose that is because the particle is 
simply carried by the fluid.
So my questions are: Is it possible there is an error in the coupling? Or what 
can I do to get the proper velocity of the particle?

Thank you,
Iva Jancigova

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Iveta Jancigova, PhD student
Faculty of Management Science and Informatics
University of Zilina, Slovakia
cell-in-fluid research group: http://cell-in-fluid.fri.uniza.sk