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Re: [ff3d-users] how to use an external mesh

From: Stephane Del Pino
Subject: Re: [ff3d-users] how to use an external mesh
Date: Thu, 19 Jan 2006 00:38:35 +0100
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Hello Pierre,

At first reading I did not noticed any mistake in your ff3d's file ...

This might be a bug in ff3d, but I am not sure about that (this is a quite 
basic test case, but one never knows ...). What does happen when your mesh is 
more refined along the Z-axis? Is it converging?
The difference with the structured case could be explained by the fact that 
structured discretization uses Q1 (hexahedra) finite element, which is exact 
for tri-affine functions ((a+x)*(b+y)*(d+z)+e) and P1 is only exact for 
affine functions (ax+by+cz+d) functions ...

Please let me know if this converges.

By the way I have a few remarks concerning your ff3d's command file:
- you should use cg instead of bicgstab: your problem is symetric, so it is 
more efficient, and you can use the ichol preconditionner if you use the 
sparse matrix storage (default is no preconditionner);
- since you are consumming to much memory you could use the 
'memory(matrix=none)' option. It is a bit slower but requires few memory. 
With this guy you cannot use 'ichol', but you can use 'diagonal' which is 
better than 'none'.


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