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## Re: [ff3d-users] Applying Boundary conditions

 From: Stephane Del Pino Subject: Re: [ff3d-users] Applying Boundary conditions Date: Tue, 5 Jan 2010 09:59:47 +0100 User-agent: KMail/1.12.4 (Linux/2.6.32-trunk-amd64; KDE/4.3.4; x86_64; ; )

```Hello again.

Le lundi 28 décembre 2009, Juzar Thingna a écrit :
> Hello Everyone,
> Below is my POV file
>
> 1   union{
> 2   box{<0,0,0>,<1000000,1,1000000>}
> 3   box {<250000,1,450000>,<350000,10000001,550000>}
> 4   box {<740000,1,495000>,<750000,10000002,505000>}
> 5   pigment {color rgb <1,0,0>}
> 6   }
>
> I have the following questions.
> 1) I need to apply Dirichlet Boundary conditions to face ymax of Box in
>  line 3 and a different Dirichlet condition to face ymax of Box in line 4.
>  Is it possible in ff3d to apply boundary conditions by specifying a plane
>  by co-ordinates rather than ymax. If so how can this be done? Box in line
>  4 is slightly larger than Box in line 3. Also if I specify the BC at ymax
>  does it apply the condition on the global ymax of the geometry ( in this
>  case it would be y=10000002) or does it apply it to the local ymax at each
>  point of the geometry?
It does not work like that in ff3d. xmin, ymin and zmin are related to the
computational mesh : not to the computational domain.

But you can define different objects of different colors (pigment {color rgb
<r,g,b>}) then apply different BC on each color as it is defined in the user
documentation.

> 2) As you can see my numbers are very large so I'll need a very fine mesh.
> Will such numbers cause any numerical errors while transferring from POV to
> ff3d?
Not in the translation but for the numerical resolution of the linear system.

Best regards,
Stéphane.

```

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