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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 |
User-agent: |
KMail/1.9.1 |
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'.
Regards,
Stephane.