Re: [ESPResSo-users] Particle in Fluid, periodic boundary conditions

Hello everybody,

I remember spotting something like this in one of the older versions of the master, but I tried to find it and could not reproduce the bug with the latest version, which one are you using?

- I am using version 3.3.0, so the latest I guess

Yes, looks like something is at odds with the periodicity here. Can you
plot the z-velocity over x-position? That may point towards what is
going wrong.

- Attached you will find the z-velocity as a function of the x-position (by accident I named it y-position). The velocity of the particle looks awkward when it gets close to the boundary (marked with a black line). I furthermore performed a simulation, where I checked the interpolated velocities of the fluid at the origin of the particle. The v_z component of the fluid looks also awkward close to the periodic boundary. Even if I don’t put particles in the fluid, I get a strange velocity of the fluid close to the periodic boundary. I was wondering, if the periodic boundary condition for the LB fluid has some bug. I played around a bit with the variable tau, but it still shows that strange behavior close to the boundary.

Does anyone has a clue where this could come from?

Attached I put some graphs of the velocity and the forces acting on the particle as a function of the position in the channel as well as the interpolated velocities of the fluid. Maybe that helps people spotting the error.

Thanks in advance.

Greetings

Markus

Von: espressomd-users-bounces+address@hidden [mailto:espressomd-users-bounces+address@hidden Im Auftrag von Joost de Graaf
Gesendet: Montag, 24. November 2014 21:25
An: Ulf Schiller
Cc: address@hidden
Betreff: Re: [ESPResSo-users] Particle in Fluid, periodic boundary conditions

Dear Markus,

I remember spotting something like this in one of the older versions of the master, but I tried to find it and could not reproduce the bug with the latest version, which one are you using?

KR, Joost

On 24 November 2014 at 19:35, Ulf Schiller <address@hidden> wrote:

Hi Markus,

On 24/11/14 18:12, Wink, Markus wrote:
> can explain it to me? It seems, that the periodic boundary condition in
> the LB Fluid doesn’t work. If I remove the fluid I don’t see that.

Yes, looks like something is at odds with the periodicity here. Can you
plot the z-velocity over x-position? That may point towards what is
going wrong.

Cheers,
Ulf

--
Dr Ulf D Schiller
Centre for Computational Science
University College London
20 Gordon Street
London WC1H 0AJ
United Kingdom

From:	Wink, Markus
Subject:	Re: [ESPResSo-users] Particle in Fluid, periodic boundary conditions
Date:	Fri, 28 Nov 2014 11:07:57 +0000