Using of 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 drawing of the geometry.

• description

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

• How to generate it with ICEM ?

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.

The meshing

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".