Re: [ESPResSo-users] Implementation of boundaries, lb_boundaries.cpp

[Stefan Kesselheim]

Hi,

On Feb 4, 2014, at 2:23 PM, "Wink, Markus" <address@hidden> wrote:

> What do you mean by " and the number is the index of the lbboundary+1"? Does 
> that mean, that the first boundary gets the number 2, the second number 3 and 
> so on (that actually happened, when I used "lbboundary print boundary")? Is 
> there any particular reason, why that is done that way? Wouldn't it be 
> sufficient just to give boundaries the flag 1, and fluid nodes the flag 0? Or 
> is there any other part in the code, where one needs that additional 
> information?

Yeah, when we want to calculate the force acting on a boundary we sum up the 
total momentum that was transferred to it in a Lattice Update. 
Therefore we need to know which boundary a node was part of.
An example is the lb_stokes_sphere.tcl test case. Here measure the force on a 
spherical object moving between two walls at a fixed velocity and compare it 
against the Stokes force.
Cheers
Stefan