[ff3d-users] Re: How to get surface mesh of different lays

[Stephane Del Pino]

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On Thursday 22 January 2004 23:47, Robert Li wrote:
> Dear Stephane Del Pino,
>   Thank you very much. You are so kindness!
>   I want to use a model which is made of three lays.
> I must get surface mesh of different lays, in order to
> set different boundary conditions at different faces.
> It was said we can use "mesh
> s1=surface(<1,0,0>,O1,M);" on Dec. 26,2003 ff3d-users
> Archives. However, I failed. Because I can not use
> above statement at all according parse.ff.yy . We can
> only use "mesh s1=surface(O1,M);".
You are right. This is the 'old' syntaxe. Now you have to proceed the 
following which is more "natural" to me...

- - you first mesh the computational domain, and then
- - extract sub meshes you need.

for instance :
domain O = domain(S, 
mesh Omesh = surface (M, inside(<1,0,0>) or inside(<0,1,0>) or 
inside(<0,0,1>));
// Omesh will now be a mesh composed of three parts [references]
// references will match your prescribed order :
//  <1,0,0> -> 1
//  <0,1,0> -> 2
//  <0,0,1> -> 3
// You can extract relevant meshes using

mesh s1 = extract(Omesh, 1);
mesh s2 = extract(Omesh, 2);
mesh s3 = extract(Omesh, 3);

// And then use the references 

solve(u) in M  //FEM
{
   pde(u)
     - div(grad(u)) = 0;
     u = -1  on s1;
     u = 0  on s2;
     u = 1  on s3;
};

You cannot use the following as you wrote:
> solve(u) in M  //FEM
> {
>    pde(u)
>      - div(grad(u)) = 0;
>      u = -1  on s1 zmax;
>      u = 0  on s1 zmin;
>      u = 1  on s3 zmax;
>      u = 2  on s3 zmin;
> };
The code must crash there [not implemented yet]. You can only use [xyz]
{min,max} with the structured background mesh! This is not a problem since 
you can still be more precise concerning your domain definition ...

Regards,
Stephane.

- -- 
Stéphane Del Pino          Tel: (33)144277170 - Fax: (33)144277200
Laboratoire Jacques-Louis Lions - Université Pierre et Marie Curie
- -+-
http://www.freefem.org
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