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

[Stefan Kesselheim]

Hi,

On Jan 30, 2014 6:20 PM, "Wink, Markus" <address@hidden> wrote:
>
> Hi everybody,
>
> I am quite sure, that the solution has converged. Attached you will find a 
> figure showing the maximum velocity as a function of the integration steps. 
> For me, it looks at is has converged. What do you say.
>
> Just to be clear: if I want a channel width of 50 with a_grid=1, I put the 
> walls at positions 1 and 51 having a box length of 52?

Absolutely. Whatever is written in Georgs thesis.

Cheers
Stefan

>
> Greetings Markus
> ________________________________________
> Von: address@hidden address@hidden&quot; im Auftrag von &quot;Stefan 
> Kesselheim address@hidden
> Gesendet: Donnerstag, 30. Januar 2014 14:57
> An: address@hidden List
> Betreff: Re: [ESPResSo-users] Simulation of fluid using LB-method
>
> Hi everybody,
> please forgive me, but is it clear that the solution is converged? Markus, 
> have you tried running for twice (or half) as many steps, and checked that 
> you get exactly the same results?
> Because near the boundary the curvature looks perfect and closer to the 
> center I'm not sure.
>
> Let me make one thing clear. With our staggered grid the position of the node 
> (m,n,o) is at m+0.5, n+0.5, o+0.5. This means if you lbboundary is located at 
> z=1, it means there is a layer of wall nodes at x=*, y=*, z=0.5. For not too 
> high viscosities (should be in the He formula as well) no measurable slip 
> should appear and the hydrodynamic boundary should be located mid-grid, thus 
> at z=1.
> If you place a boundary at - say - 0.8, the hydrodynamic boundary of course 
> is still at 1.
>
> I'm not sure, Markus, if you put these parameters correctly into you 
> theoretical curve. We introduced the staggered grid some time after Georg's 
> bachelor thesis to allow for using a nonzero skin with LB.
>
> Cheers
> Stefan
>
> On Jan 30, 2014, at 2:47 PM, Ulf Schiller <address@hidden> wrote:
>
> > On 01/30/2014 02:33 PM, Georg Rempfer wrote:
> >> Hey all,
> >>
> >> I remember that we fixed the issue with the missing 0.5*h*F some years
> >> ago. For a flat bounce-back wall aligned with the lattice axis, the
> >> actual hydrodynamic no-slip wall is positioned in the middle between the
> >> last fluid node and the first wall node.
> >
> > There is still a viscosity dependent slip velocity, cf. Eq. (20) in [He et 
> > al. (1997), J. Stat. Phys. 87, 115].
> >
> > Cheers,
> > 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
> >