[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ESPResSo-users] Lattice Boltzmann External Force

From: Georg Rempfer
Subject: Re: [ESPResSo-users] Lattice Boltzmann External Force
Date: Thu, 09 Feb 2012 20:52:55 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111229 Thunderbird/9.0

Hello Wolfgang,

thank you for your effort. Owen Hickey and I were actually working on tracking down and fixing this bug yesterday. We agree with you on the fact that it is not a simple discretisation artifact since it does not occur in the gpu implementation.

Also as far as I understand the LB populations are accessible from the TCL level via the "lbnode x y z print pop" command in the CPU implementation. Unfortunately the GPU implementation does not contain this feature.

Dominic (if you are on this mailing list): I wanted to ask you anyways whether you could implement that for us. Is this possible or would it take too much time?

Georg Rempfer

Am 09.02.2012 14:28, schrieb Wolfgang Riefler:
Hello everyone.

First of all thanks for all your quick answers.

I probably should have said before that the offset I was getting was in
the range of many times the maximum velocity (a maximum velocity of 0.04
had an offset of 0.5), so I don't think its because of the discrete
boundaries. Just to be sure I checked the simulation again for a very
small viscosity and I still get the offset.

At the moment I am working with the version 3.0.2.

Coming back to the original problem, it was actually the PhD thesis of
Ulf "Thermal fluctuations and boundary conditions in the lattice
Boltzmann method" that caught my eye and made me change the source code,
since it says in equation (4.65):

                               j = j' + 0.5 * g * tau

where j is the hydrodynamic momentum density, g is the volumetric force
and tau the lattice boltzmann time step.

Implementing this line, I get a much better result, with only a little
offset, which is probably due to the discrete boundary.

Thanks again for your help,


reply via email to

[Prev in Thread] Current Thread [Next in Thread]