[RodriguezFatz]

Hi all,

I only used ICEM up to now and I am currently trying to get Ansys Meshing running. The problem is, I have an imported CAD geometry, with many "unnecessery" edges on the surface. During meshing I want the mesher to ignore these edges, thus I don't want to have points on all these edges.
I hope the picture shows what I want. The red lines show the edges from the CAD model, where I don't want the mesher to place the nodes...
pic.jpg
What is the easiest way to get rid of this?

Thanks for any help!
Philipp.

[Antanas]

Originally Posted by RodriguezFatz

Hi all,

I only used ICEM up to now and I am currently trying to get Ansys Meshing running. The problem is, I have an imported CAD geometry, with many "unnecessery" edges on the surface. During meshing I want the mesher to ignore these edges, thus I don't want to have points on all these edges.
I hope the picture shows what I want. The red lines show the edges from the CAD model, where I don't want the mesher to place the nodes...
Attachment 43415
What is the easiest way to get rid of this?

Thanks for any help!
Philipp.

Use patch independent algorithm.

[RodriguezFatz]

OK. What do I need to click in which order? Come on, I'm a compleet rookie.

[Gweher]

Hi Philipp,

You have various options. You can either :

- edit the imported geometry within design modeler using the merge tool option (under Tools > Merge > select the faces > generate)

- Use the defeaturing method by specifying the smallest "detail" you want to mesh (under mesh > Defeaturing > Defeaturing Tolerance )

- Create a virtual topology that allows you to virtually merge faces for the meshing procedure. For this you need to insert a virtual topology ( rmb on Model > Insert > Virtual topology then in the graphics window select the faces > rmb > insert > virtual cell)

Have fun

[RodriguezFatz]

Hey, thanks for the input.
I think I can also choose meshing method "tetrahedrons" and then "Patch Independent", which will do what I need, correct? I think this is what Antanas meant.

One question to your third point: If I create these virtual topologies, it looks like what I want: The edges are deleted. But do the old surfaces remain, or does it compute new interpolated surfaces? This would be important to me, because I don't want large changes in the geometry.

[Gweher]

Yes you can use the tetrahedrons method with patch independent algorithm (Mesh > inert > method > tetrahedrons > patch independent under algorithm tab). This is what Antanas mentioned and it works without any problem.

Virtual topology will not modify the original geometry, but depending on the complexity of the edges/surfaces it need to "stitch" the topology and it will certainty need some interpolation so in your case you need to go with the patch independent algorithm

[RodriguezFatz]

Hi again, I some new questions:

Here you see a part of the housing (gray) and the air inside the housing (green). These are different parts.
file - Kopie.jpg
1. Can I change the colors of these parts?
2. When using the patch independent algorithm as suggested, is it possible to have rather large cells on the surface of the housing but a finer mesh inside the wall of the housing? The wall of the housing is pretty thin, as you can see, but I need a fine mesh from outside to inside to account for heat flux through the wall. When I just change the overall cell size, meshing jumps into maniac mode and of course creates a very large mesh.

[Gweher]

Hi again,

1. Can I change the colors of these parts?

Well in AM the colors are generated by default. In order to change them you need to go in the geometry tree, highlight the part you want to change > Graphics Properties > Color > and click on the "..." and pick the color you want. Then generate the mesh. If you have already generated the mesh previously then you need to clear the generated data by rmb on mesh > Clear generated data and generate the mesh again.

2. When using the patch independent algorithm as suggested, is it possible to have rather large cells on the surface of the housing but a finer mesh inside the wall of the housing? The wall of the housing is pretty thin, as you can see, but I need a fine mesh from outside to inside to account for heat flux through the wall. When I just change the overall cell size, meshing jumps into maniac mode and of course creates a very large mesh.

If you want to have more cells inside your wall the easiest way is to inflate the tetrahedron method previously inserted, rmb on the method > inflate this method select the body (here your thin wall) then under boundary select the boundary edges. You can choose the number maximum number of layers that you want with a specific growth rate.

Voila

[RodriguezFatz]

Hi again,

I have another question about the meshing.
file.png
Right now, the inflation layer works in the fluid region. In the solid region I use the same setting (first layer height), but the whole inflation layer is completely flat. Please see the picture. Both have setting 1e-4 for first layer height. You can see, that the solid is pretty thin. There is only one layer of regular cells above the inflation layer. I guess this is the reason, why the inflation is so thin.
Is there any way I can get the inflation layer go through the whole solid body, from one side to the other? Or force the inflation layer to become bigger?

Philipp.

[Gweher]

Hi Philipp,

If you applied the same principle for the fluid mesh to the solid one then you can play with inflation layer parameters such as :
- the numbers of layers
- initial height (here you specified 1e-4)
- transition ratio

If you want to decrease the size of the "regular cells above the inflation" then you can increase the numbers of layer and reduce the transition ratio to obtain a smoother transition inside of your solid.

Have a nice day

[RodriguezFatz]

I didn't explain this good enough.
Can I get a prism layer through the whole solid? As the orange cells in the picture?
file.png

[Gweher]

In this case you can change the inflation option, instead of smooth transition use "total thickness" and specify the thickness of your solid. Changing this option allows you to increase the prism layers total height and it should give you the orange mesh you mentioned.

[RodriguezFatz]

Thanks for your help!
Unfortunately, I was not successful.
I tried to play with different "collision avoidance" settings.
Standard is "layer compression" which leads to the picture above, no matter if I set total thickness or first layer thickness - the inflation layer is always compressed.
Setting "Stair Stepping" leads to no inflation layer at all in the solid.
With setting "none" the mesh creation fails.

Any ideas how to force the mesher to do what I want ?

[RodriguezFatz]

Yeeehaaa!
It was the f**** gap factor. I set it to "0", now it works.

[Gweher]

Hi Philipp,

Sorry for my late comment, was quite busy during the last week. Well you solve it by yourself. The default gap factor is 0.5 for the tetrahedron method, with 1 corresponding to the ideal tetrahedral cell height. If you use a value of 0 it allows you to play freely with the cell height and number of inflation layers.

Have a nice day !

[RodriguezFatz]

Hi again,
I have still one thing to figure out:
It still does not inflate the whole solid body, there will always remain one layer of tetrahedral elements on top of the layer. If I inflate "from both sides", there will always be one layer of tetrahedrals in the middle of the solid. Of course, these elements are highly skewed, because they are incredibly flat.
Do you know any trick to get rid of that last layer?

[Gweher]

That's strange, do you mind sharing your .wbpj files ?

[RodriguezFatz]

It's some confidential stuff from my company... I just created a service request on Ansys website. I will post the result.

[Antanas]

Originally Posted by RodriguezFatz

Hi again,
I have still one thing to figure out:
It still does not inflate the whole solid body, there will always remain one layer of tetrahedral elements on top of the layer. If I inflate "from both sides", there will always be one layer of tetrahedrals in the middle of the solid. Of course, these elements are highly skewed, because they are incredibly flat.
Do you know any trick to get rid of that last layer?

It's not good idea to use inflation for your purpouse. Is that solid body sweepable? If so use sweep meshing method. If not then think maybe you can make it sweepable. Also you may try to use multizone method.

[RodriguezFatz]

Hi,
Ansys support: What I want to do doesn't work. Inflation always has that layer of hexaedral elements on top, I can not prevent it from doing this.

I still think inflation would be perfect for that purpose, because you don't have to manipulate the geometry. And it is any easy way to get a fine resultion perpendicular to the wall and a coarse resolution parallel to the wall. I don't know why Ansys forces this last layer on top.
How comes you don't like it?

Yes, I think I have to cut the model in pieces.