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## Re: [ESPResSo-users] Simulation of fluid using LB-method

 From: Stefan Kesselheim Subject: Re: [ESPResSo-users] Simulation of fluid using LB-method Date: Thu, 30 Jan 2014 15:26:22 +0100

```Hi,
lbboundary wall normal 0 0 1 dist [expr \$agrid]
lbboundary wall normal 0 0 -1 dist [expr -\$l-\$agrid]
Cheers
Stefan

On Jan 30, 2014, at 3:23 PM, "Wink, Markus" <address@hidden> wrote:

> Hello,
>
> Well in the case of the a_grid=0,5 I chose in my tcl-script:
>
> "
> set l 51.5
> setmd box_l \$l \$l \$l
> [...]
> set agrid 0.5
>
> lbboundary wall normal 0 0 1 dist [expr 1.5*\$agrid]
> lbboundary wall normal 0 0 -1 dist [expr -\$l+1.5*\$agrid]
>
> [...]
> "
>
> So I changed it, didn't I. Still puzzled, why it doesn't work.
>
> Markus Wink
>
>
>
> -----Ursprüngliche Nachricht-----
> Gesendet: Donnerstag, 30. Januar 2014 15:12
> Betreff: Re: [ESPResSo-users] Simulation of fluid using LB-method
>
> On 01/30/2014 03:03 PM, Wink, Markus wrote:
>> Hello everybody,
>>
>> I tried to think about of the real position of the wall:
>> "The (0, 0, 0) node of the LB lattice in Espresso is placed at (agrid/2,
>> agrid/2, agrid/2)."
>> In my case, I chose a_grid =1, so I put the walls at 1.5 and 51.5 in the
>> simulation box. Thus the length of the simulation box is 53 in my case,
>> gibing a channel width of 50.
>
> In that case the actual locations are 2.0 and 51.0, if I'm not mistaken
> (Georg?). Then the width is 49.0 which would bring your v_max*50/49
> close to the theoretical value.
>
> Best,
> Ulf
>
> --
> Dr. Ulf D. Schiller                        Building 04.16, Room 3006
> Institute of Complex Systems (ICS-2)       Phone:   +49 2461 61-6144
> Forschungszentrum Jülich, Germany          Fax:     +49 2461 61-3180
>

```