Re: [ff3d-users] Setting boundary conditions!!

[Arun Viswanathan]

Hi Stephane!!

A couple more issues....

1. I will need to add one more boundary condition to
my code. Among the 12 cylinders, incase 1 (or more) of
them leak, I would like to pass this as a boundary
condition as well. That is, the leak will simply act
like a source for the entry of the substance into the
container, and I would like to define the source among
the boundary conditions. How can I do this??

2. Also, how can I pass this information (regarding
the source of leak) to the code, without hard-coding
it. I plan to determine the rate at which the chemical
escapes from the leak using another formula. How can I
do that here, can I code it in C?? Or should it be
some other language, like Java or Perl?? I tried using
'printf' and 'cout' before, they didn't work!! So how
can I add other code??

Thanks, best regards,
Arun.

--- Stephane Del Pino <address@hidden> wrote:
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> Le mardi 25 Mai 2004 22:30, Arun Viswanathan a
> écrit :
> > Hi all,
> >
> > sorry to be bothering you all again.  But please
> do
> > take some time of to go through the issue here.
> I'd
> > appreciate as many suggestions as possible, coz I
> need
> > all the help possible here.
> >
> > The problem that I am trying to solve involves a
> > container carrying several drums, each drum
> consisting
> > of gases. Incase any of the drums leaks, I would
> like
> > to determine the concentration of the gas (as it
> > diffuses into the rest of the container) in
> different
> > pats of the container.
> >
> > 1. The trivial case to consider here is if there
> are
> > no drums, and I just want to determine the
> > concentration in different parts of the container.
> In
> > this case, the boundary condition will be that the
> > rate of change of concentration in the direction
> > normal to the container's walls is zero. So my
> > question is, how to set the condition as: dC/dx =
> 0
> > for a wall perpendicular to the x-axis and dC/dz
> -= 0
> > for a wall perpendicular to the z-axis??
> You have to use the syntax
>       dnu(C) = 0 on M foo;
> where foo is one of xmin,xmax,ymin,ymax,zmin,zmax.
> But since this condition is 0, you can omit it, it
> will be naturally taken 
> (see FEM theory for details).
> 
> > 2. The not-so-trivial case would involve the drums
> > within the container. Here, any gas that leaks
> (from a
> > drum) would find its way around the container
> (through
> > diffusion). But the additional boundary conditions
> I'd
> > have to provide here would be, if the gas hits a
> wall
> > of any of the drums, then the change in
> concentration
> > normal to that direction would be zero. How do I
> set
> > these conditions for the drums' walls??
> This is exactly the same thing. Imposing nothing
> will provide homogeneous 
> Neumann conditions.
> 
> Regards,
> Stephane.
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