Re: [ff3d-users] Inner wall definitions

[Stephane Del Pino]

Hello Emilio.

I think you need some enlightenment about the fictitious domain method that 
you are using in the ff3d:

A fictitious domain method consists in using a mesh that does not match the 
geometry of the problem that you want to solve.

For instance look at the attached picture. Suppose that you want to solve a 
problem in the blue domain (left part). The fictitious domain method will use 
a cartesian mesh to solve the problem. With ff3d's approach, only the blue 
cells will be used for the computation: some vertices (outside of the domain) 
are needed to build a good approximation of the solution inside the domain.

So (to simplify, in fact it is a bit more tricky) you can consider that when 
you use the tetrahedrize keyword, you do not see the geometry of the domain, 
but all the cells that are used to compute the solution.

Post-processing of fictitious domain approximation is not an easy task: often, 
the solution is better than it looks like...

Best regards,
Stéphane.

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