__Using of ICEM__

**description****How to generate it with ICEM ?**

This part deals with the different steps necessary to
perform the meshing of the air filter on ICEM : the drawing of the geometry,
the blocking, and the meshing.

This does not clame at all to be a user guide or anythingelse
, but simply a summary of our work and difficulties we met.

It is obvious that simple geometries such as an air filter
do not require a complex mesher like ICEM. Meshers like Gambit or even

PreBfc are much more adapted and quick.

However, through this simple application, we were able
to encounter many characteristical difficulties of ICEM which we would
not be able to solve with a complex geometry.

The geometry is an air filter. This picture shows a 2D view
of it , but actually it is an axisymetric device .

Consequently, we only had to generate a 2D geometry and to
declare it "axisymmetric" in Fluent5.

One can give the following description :

1 : inlet of the air flow

2 : wall or porous media with low permeability

3 : porous media with medium permeability

4 : outlet of the air flow

5 : wall

6 : axis of symmetry

The generation is done with DDN.

Above all, one must create all the points composing
the geometry : by using the mouse or by entering the coordinates.

Then, these points must be linked with curves.

Finally, if it is a 3D geometry, these curves must be linked
with surfaces.

Moreover, domain points have to be created within each fluid
domains.

**Caution** : it
is very important to think about the way your geometry will be split in
blocks during the blocking step.

Indeed, during the projection step, the blocks verteces can only be projected
on points of the geometry.

Thus, during the drawing step, it is necessary to create all the
points and all the curves which will be useful

during the projection step.

The second step requires to define families (inlet, outlet,
wall, intern, fluid, porous...), and to store the different curves and

domain points of the geometry in them.

That is the list of the families we created :

- inlet

- outlet

- wall

- symmetry

- porous 1 et 2 (according to the kind of air filter studied)

- intern

- fluid

**Caution** : It is necessary
to create a family named "fluid".

All
the curves inside the domain which are not walls must be gather in the
same family (intern for example), because

they
will need to be declared as "interior" for Fluent5.

__The blocking and the projection
steps__

After having generated the geometry and in order to prepare
the projection step, it is necessary to split it in rectangular blocks.

The following picture shows it .

Then, one can group the little blocks and create several bigger ones. But, it is important that a block is not part of two different domains.

**Caution** : No projection
must be done on the entities of the family declared "interior"
for Fluent5. Indeed, it changes them in wall.

Consequently, it is necessary that the blocks exactly superpose with
the curves of this family.

The next step consists in associating each blocks with the domain fluid which it is part of : porous 1, porous 2, fluid, or vorfn (orfelin volume : volume of the domain which does not require to be meshed).

Finally, one must project the blocks on the curves of
the geometry.

When the blocking and projection steps are finished, it is sufficient to run the meshing option to get the meshing.

Then, one can modify the number of cells on each curves.
Thus, one can obtain a meshing adapted to the geometry

and to the physical problem to be simulated. For example,
we tightened up the meshing in the porous media.

Finally, the last step consists in configurating the meshing
with the solver chosen for the simulation. In our case, it is Fluent5.

It is therefore necessary to associate the good boundary
conditions of Fluent5 with each family of curves.

**Caution** : the family
called "intern" must be associated with the boundary condition
"interior".