[ESPResSo-users] Lattice Boltzmann boundaries in Espresso 3.1

[Wolfgang Riefler]

Hi All,

I have recently switched from Espresso 3.0 to 3.1 (Congrats to the new version by the way).

To test if everything is going well, I wanted to simulate a simple Poiseuille flow between two walls, thus defining

setmd box_l 40 40 40
lbboundary wall dist 0.0 normal 0.0 1.0 0.0
lbboundary wall dist -32.0 normal 0.0 -1.0 0.0

which should give me two plane walls in the x-z plane at y=0 and y=32.

According to the Espresso manual (and simulations done with Espresso 3.0), it will result in two effective boundaries at y~0.5 and y~31.5.

I set the fluid to 

lbfluid agrid 1.0 dens 1.0 visc 3.0 tau 0.001 ext_force 0.001 0.0 0.0 friction 20.0
thermostat lb 0.0

and start integrating until the solution has converged well enough.

Surprisingly I get effective boundaries at y~-0.5 and y~31.5, which means that y=0 is no boundary node. 

I have read in the NEWS file that the boundaries have been worked on for Espresso 3.1, so am I missing something?

Thank you very much in advance,

best,

Wolfgang