Re: [ESPResSo-devel] Moving Wall

[Axel Arnold]

Hi!

On Wednesday 29 December 2010, MEHMET SAYAR wrote:
> Hi All,
> 
> I want like to implement something like a moving wall.
> Basically I have a target particle A, and I want the other particles to
> remain below the z-coordinate
> of particle A.
> 
> Is there any feature like this already in Espresso?

Not that I am aware of. It is also a bit of a tricky idea, since the forces 
acting on this wall are ignored. Normally, one can argue that the wall has 
infinite weight, but in your case, it is coupled to a particle.

> I though about implementing a moving wall, where the distance of the wall
> is
> matched to the z-coordinate of particle A. Would that be feasible?
>
> For parallel runs, I would have to update the position of the wall at all
> time steps I guess.

It is certainly feasible. Basically, you need to insert a routine in the 
beginning of the force calculation, more precisely, in init_forces() in 
forces.c. At the end, already the forces acting on the constraints are 
initialized, and at that place you could broadcast the position of the 
particle of interest to all processors to update the constraint.

Many regards and a happy New Year,
Axel

-- 
JP Dr. Axel Arnold      Tel: +49 711 685 67609
ICP, Universität Stuttgart      Email: address@hidden
Pfaffenwaldring 27
70569 Stuttgart, Germany