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-   -   [GAMBIT] Meshing 2D Fins Object (http://www.cfd-online.com/Forums/ansys-meshing/123020-meshing-2d-fins-object.html)

spartacurse September 3, 2013 00:23

Meshing 2D Fins Object
 
I intend to create a 2D mesh of a heat sink. It consists of multiple fins, an inlet and outlet.
2D model was created from AutoCad.
Iíve read and watched tutorials from

http://aerojet.engr.ucdavis.edu/gamb...ide/mg0302.htm
http://www.youtube.com/watch?v=Gub1Kbcup2k

I managed to create faces of each fins. I just intend to mesh the fluid region outside the fins and the inlet/outlet. How do I go about doing this?

Beginner here, hope to learn this.

http://i.imgur.com/0iVLEfl.png

http://i.imgur.com/bz7jC7f.jpg

-mAx- September 3, 2013 01:44

*why are you meshing the fins? As you said you need to mesh the fluid domain around the fins.

*Split you domain for a better control of the mesh. For instance if you split your domain at top and bottom of you fins, you will isolate the upper part (with upper hole), lower part (with lower hole), and all gaps between fins.
Then just mesh all isolated domains (2d) one by one

spartacurse September 3, 2013 05:39

Thanks for the prompt reply.

I'm still getting used to the thought process of what needs to be done.

I managed to split the domain for the top,bottom and each channel in the middle.

However, for the bottom/top domain, it meshes the whole face including the outlet. How do I go about just meshing the top/bottom domain without the inlet/outlet?

http://i.imgur.com/dA3AMgh.jpg

-mAx- September 3, 2013 05:48

that's because you didnt split the hole from your surface.
For being sure of your topology switch to shaded mode. You will see if your holes are hollowed (or not)
You also have a problem at your splits top and bottom. Thus if I see your bottom-mesh, then all extremities from fins should also belong to bottom domain. In your case, all vertices (from fin's extremities) aren't part of your domain (understand from those vertices you should have a "mesh")

spartacurse September 4, 2013 01:55

I increased the distance of the top/bottom domain from the fins, such that the extremities would be associated with the fins. Hope I got what you meant.

http://i.imgur.com/V6WRk5k.jpg

However, I am still unable to mesh the middle fluid fin boundary. Gambit is killed after awhile due to the runs being longer than my cpu time limit.

Is there another way to do this?

http://i.imgur.com/3DodzIz.jpg

-mAx- September 4, 2013 02:05

your previous split was better, because you had the possibily to handle every gap between fins with quad/map.
Check with shaded mode if all your fins appear as hollow
If you want I can check your geometry (just provide the dbs file)

spartacurse September 4, 2013 02:16

https://www.dropbox.com/s/pph4nj81z0...luiddomain.dbs

I can't upload it to the forum so I shared through dropbox. This was the file before Gambit was killed.

-mAx- September 4, 2013 03:00

2 Attachment(s)
From your dbs:
*Merge Faces.54 and Faces.57 > it gives your Faces.54
*Merge Faces.54 and Faces.53 > it gives you Faces.54
*Copy Vertex.410 and Vertex.312 with Vector (10 0 0) > it gives you vertex.415 and vertex.416
*Copy Vertex.413 and vertex.411 with vector (-10 0 0 ) > it gives you vertex.417 and vertex.418
*Create straight edge with vertex.417 and vertex.415 > it gives you edge.417
*Create straight edge with vertex.416 and vertex.418 > it gives you edge.418
*split face.54 with edge.417
*split face.54 with edge.418
>> that's it you can mesh
Attachment 25049 Attachment 25050

spartacurse September 4, 2013 04:04

1 Attachment(s)
I managed to re-create the proper geometry. Thanks for the tip on using the split/merge functions.

I meshed the upper/bottom boundary first.

selected the individual planes in the middle boundary but couldn't use a quad/map between the fin gap. I do not know how you linked the meshes between the top/bottom and the gaps between the fins.

I understand that it has to do with "vertices should have a mesh"

-mAx- September 4, 2013 04:09

Quote:

Originally Posted by spartacurse (Post 449741)
I meshed the upper/bottom boundary first.

wrong
mesh gap between fins first
In your case you already meshed top and bottom surfaces from fins. If both edges don't have same node count, then you cannot use map scheme
PS: this is exactly the error you get ;)

spartacurse September 4, 2013 04:47

1 Attachment(s)
I am not sure what i'm doing that is causing my "edges" to not have the same node count

I tried meshing the gaps first this time before the top/bottom boundary.

-mAx- September 4, 2013 04:50

Mesh all the subdomains between fins with quad/map, because they are rectangles
But mesh top and bottom domains (with hole) with quad/pave.

spartacurse September 4, 2013 04:57

I see now. All is good. Thank you for your patience.

spartacurse September 8, 2013 23:34

1 Attachment(s)
Hi again,

I modified the design such that the inlet/outlet are edges at the side of the heat sink (on the right in this case).

I specified both edges as the necessary boundary zones. After exporting the mesh, I encountered this error.

WARN: Boundary Entity mass_flow_inlet.1 does not contain any valid entity
WARN: Boundary Entity outlet does not contain any valid entity

However I already checked that the entities are the specified edges respectively.

-mAx- September 9, 2013 00:57

are they meshed?

spartacurse September 9, 2013 01:05

Yes I meshed both edges prior to exporting it.

The edges are drawn in addition to the the edge that I drew with the figure.

-mAx- September 9, 2013 01:08

*did you enable 2d option while exporting?
* check if you don't have duplicate edges on those inle-outlet
* Else post a picture of your domain with mesh, and dsplay where are those inlet-outlet

spartacurse September 9, 2013 01:41

solved the issue: I had duplicate edges. learning something new everyday.:o

Deleted the edge on the right and separated edges. I'm able to export properly again now. thanks!

spartacurse September 15, 2013 23:59

1 Attachment(s)
hi again.

i've separated the top/bottom and the channel into different boundaries for another design.

however, the meshes did not connect/link when i export it out. I'm not sure what I did wrong here.

-mAx- September 16, 2013 01:00

Clearly a connectivity problem
try to connect edges (/All)
If it is not successfull , then you will need to split the "long" edge from bottom domain with each "small" edge from channels (one by on), and after again a connect /all


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