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actone October 23, 2006 05:50

2D MESH
 
Hi i'm working on a 2D mesh and i wonder if the size of the extruded 2D mesh is important or not.

thanks in advance.

Camilo Costa October 23, 2006 14:23

Re: 2D MESH
 
GENERALLY, THE DISTANCE OF SIMETRY FACES ARE THE SAME LENGHT OF YOUR SMALL VOLUME MESH!!

actone October 24, 2006 04:51

Re: 2D MESH
 
thanks Camilo

my smallest volume is about 3e-3mm (my Re is 1.2e-6 so i need a very small first layer in my BL). isn't it too small? (the geometry is 150mm long) i've made an unsteady computation with 1mm of thickness and it seems to become 3D (that was the reason my question in fact, when i look at the pressure at the two periodic faces, it's the same at the beginning and then it become very different )

note: i extrude 1 layer thinck in CFX mesh with extruded periodic pair, then i set two symetry BC in CFX pre. is that right?


Camilo Costa October 24, 2006 13:56

Re: 2D MESH
 
I think no, but a problem that you can have is, if you use a ICEM for construction your mesh, when you import your geometry same lines and points can disappear. This is a bug of program!! For solution this construct your geometry in ICEM, is a shit, but work.

If you use CFX mesh you donīt have problem, but icem is more difficult to use for construction.

TB October 26, 2006 21:55

Re: 2D MESH
 
CFX thought is to treat ICEM as a meshing tool, I think. Load your model into the workbench, and modify from there. Lots of powerful solid modelling software are now available on the market.

CFX mesh doesn't offer hex mesh tool, if my information is still valid. For a simple 2D problem, I will suggest the use of hex mesh.

Robin October 27, 2006 09:59

Re: 2D MESH
 
CFX-Mesh does have a pseudo 2D meshing option which will output one or multiple layers. In CFX-Mesh, go to Model>Mesh>Options and switch Meshing Strategy from Advancing Front and Inflation to Extruded 2D Mesh.

Once you have made this change, the Periodicity object will disappear and be replaced by the Extruded Periodic Pair object. Pick the start and end faces of your geometry as the periodic pair. If the geometry is axisymmetric you must also include the axis of rotation. Change periodic type to Rotational and select or edit(by right clicking on Point) the two points that define your axis.

2D Extrusion Option = Full will extrude the face mesh through your entire model and divid it into the specified number of layers.

2D Extrusion Option = Partial will extrude the mesh one layer and automatically calculate the thickness based on your mesh size to be optimum for the solver.

The final mesh will be a combination of hexes (at inflation layers) and prisms, both of which are good for 2D simulations.

Regards, Robin


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