Fluent gets rid of interior boundaries

mike.franky · August 29, 2012, 13:26

Hi,

I am relatively new to Ansys ICEM and Fluent so this might be an obvious question for some.

Basically I am trying to create two boxes (in 3D). The two boxes are of different sizes and the smaller one is placed inside of the larger one. To me this seems quite a straight forward task in icem. However, when FLUENT reads the exported file it only detects the outer box and completely disregards the inner one.

I have checked the .msh file produced by ICEM which does not include any information regarding the smaller, inner box, so I suppose the problem is during the exportation!

If anyone has a clue of what might be going on I would be very grateful.

Thanks in advance

yonchong · August 29, 2012, 16:57

Try to define the internal surfaces inside ICEM before exporting to Fluent.

Output -> Boundary conditions -> Surfaces -> Two-sided -> Create new -> interior

mike.franky · August 30, 2012, 05:58

Hi yonchong and thank you very much for your reply.

So far I had the boundary condition as wall. I tried what you said (i.e. setting the interior boundary condition) but without any effect.

Any other ideas?

Thanks again

siara817 · August 30, 2012, 06:06

How if you generate two seperate boxes in ICEM and import the two meshes into the Fluent. Have you tried that?

mike.franky · August 30, 2012, 06:12

Hi siara817 and thanks for your response

I haven't actually tried what you said. I sounds like a very good idea. I will try it out and let you know what happens.

However, as I am trying to familiarise myself with these pieces of software, it would be great if someone could still shine some light onto where I am messing things up

siara817 · August 30, 2012, 06:16

I look forward to seeing if it worked for you. I think the reason of removing the interior box is, that ICEM generates mesh for the main box and ignore small box. If you could determine in ICEM to generate mesh seperately for every box, then I think it will be solved.

mike.franky · August 30, 2012, 06:37

Have in mind that when I do the same thing in 2D (i.e. square within a square) everything works fine!

By the way, how can I import two separate meshes in fluent?

yonchong · August 30, 2012, 07:29

Could you upload the file so I can have a look?

By the way, you did create a body for each boxes?

mike.franky · August 30, 2012, 07:59

Which file would you like me to upload? the project file?

Yes I did add a body for both boxes.

yonchong · August 30, 2012, 08:56

Just the tin file.

mike.franky · August 30, 2012, 10:16

I am attaching the .tin file for the mesh!

Thanks

yonchong · August 30, 2012, 10:21

Nothing in the zip file.

mike.franky · August 30, 2012, 10:22

Sorry about that... try again

yonchong · August 30, 2012, 10:47

The grid is very coarse but I did no find any problem.

I created a volume and surface mesh together using Octree.

Output -> Boundary Conditions

and set the surfaces_heater as an interior (not interface).

Output -> Write input

to create fluent.msh.

Read into Fluent and it created a surface called "int_surfaces_heater".

mike.franky · August 30, 2012, 10:58

Thanks again for your reply.

I haven't refined the mesh yet as I am first trying to get everything working but you are right! It needs a lot of work.

Regarding the problem, I have changed the boundary conditions to interior and wrote the output. However the problem persists! Did you manage to make it work?

yonchong · August 30, 2012, 11:26

I haven't touched a thing but it worked for me.

mike.franky · August 30, 2012, 11:57

I must be doing something wrong when I output it for fluent then! I just select fluent v_6 for solver and then I write to output. Is there anything else I should be doing?

yonchong · August 30, 2012, 12:29

No. It will ask for uns file you want to use and will write out a fluent mesh file.

By the way, the interior surface will have name changed with prefix of "int_".

mike.franky · August 30, 2012, 12:38

this is very strange! This is exactly what I am doing! In fluent I get an int_liquid, where liquid is the material point of the larger box, and surface_bath which is the large box itself!

yonchong · August 30, 2012, 15:14

I am posting a screenshot.

You can see the int_surface_heater which is the interior type boundary condition.

August 29, 2012, 13:26	Fluent gets rid of interior boundaries	#1
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Hi, I am relatively new to Ansys ICEM and Fluent so this might be an obvious question for some. Basically I am trying to create two boxes (in 3D). The two boxes are of different sizes and the smaller one is placed inside of the larger one. To me this seems quite a straight forward task in icem. However, when FLUENT reads the exported file it only detects the outer box and completely disregards the inner one. I have checked the .msh file produced by ICEM which does not include any information regarding the smaller, inner box, so I suppose the problem is during the exportation! If anyone has a clue of what might be going on I would be very grateful. Thanks in advance

August 30, 2012, 10:47	No problem found	#14
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	The grid is very coarse but I did no find any problem. I created a volume and surface mesh together using Octree. Output -> Boundary Conditions and set the surfaces_heater as an interior (not interface). Output -> Write input to create fluent.msh. Read into Fluent and it created a surface called "int_surfaces_heater".

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August 29, 2012, 16:57		#2
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	Try to define the internal surfaces inside ICEM before exporting to Fluent. Output -> Boundary conditions -> Surfaces -> Two-sided -> Create new -> interior

August 30, 2012, 05:58		#3
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Hi yonchong and thank you very much for your reply. So far I had the boundary condition as wall. I tried what you said (i.e. setting the interior boundary condition) but without any effect. Any other ideas? Thanks again

August 30, 2012, 06:06		#4
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 18	How if you generate two seperate boxes in ICEM and import the two meshes into the Fluent. Have you tried that?

August 30, 2012, 06:12		#5
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Hi siara817 and thanks for your response I haven't actually tried what you said. I sounds like a very good idea. I will try it out and let you know what happens. However, as I am trying to familiarise myself with these pieces of software, it would be great if someone could still shine some light onto where I am messing things up

August 30, 2012, 06:16		#6
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 18	I look forward to seeing if it worked for you. I think the reason of removing the interior box is, that ICEM generates mesh for the main box and ignore small box. If you could determine in ICEM to generate mesh seperately for every box, then I think it will be solved.

August 30, 2012, 06:37		#7
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Have in mind that when I do the same thing in 2D (i.e. square within a square) everything works fine! By the way, how can I import two separate meshes in fluent?

August 30, 2012, 07:29		#8
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	Could you upload the file so I can have a look? By the way, you did create a body for each boxes?

August 30, 2012, 07:59		#9
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Which file would you like me to upload? the project file? Yes I did add a body for both boxes.

August 30, 2012, 08:56		#10
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	Just the tin file.

August 30, 2012, 10:21		#12
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	Nothing in the zip file.

August 30, 2012, 10:58		#15
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	Thanks again for your reply. I haven't refined the mesh yet as I am first trying to get everything working but you are right! It needs a lot of work. Regarding the problem, I have changed the boundary conditions to interior and wrote the output. However the problem persists! Did you manage to make it work?

August 30, 2012, 11:26		#16
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	I haven't touched a thing but it worked for me.

August 30, 2012, 11:57		#17
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	I must be doing something wrong when I output it for fluent then! I just select fluent v_6 for solver and then I write to output. Is there anything else I should be doing?

August 30, 2012, 12:29		#18
yonchong Member Yon Han Chong Join Date: Jun 2012 Posts: 77 Rep Power: 14	No. It will ask for uns file you want to use and will write out a fluent mesh file. By the way, the interior surface will have name changed with prefix of "int_".

August 30, 2012, 12:38		#19
mike.franky Member Michael Frank Join Date: Aug 2012 Posts: 55 Rep Power: 14	this is very strange! This is exactly what I am doing! In fluent I get an int_liquid, where liquid is the material point of the larger box, and surface_bath which is the large box itself!