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Flaky October 7, 2010 05:38

Sub-domain Confusion
 
Hi all,

I am currently experiencing some confusion over the setting of my sub-domain boundary condition. My initial questions were mention over at another thread which can be found here.

My aim is to model a tunnel dimensions 150m long 10m wide 8m high, with a localize heat source model as a void in the picture below.
The geometry have been split using workbench geometry and suppressed before meshing.

My idea is to replace the "fire" as a heat source.

Is it require to model a solid geometry in place of the void as shown in the picture below. This would enable me to create a solid Domain and define a sub-boundary condition where i can input the heat source parameters.

Initially i have tired creating a sub-boundary vie the fluid Domain by picking the surfaces along the void. But in this case, does that means that the "sub-boundary" which is base on the fluid is releasing the heat instead?


http://img840.imageshack.us/img840/6216/finermesh.png
http://img525.imageshack.us/img525/3...meshzoomin.png

Thanks in advance for comments and advice

ghorrocks October 7, 2010 07:17

You have two choices:

1) Model the sub-domain as a fluid region and apply the heat source as a volumetric heat source. This way you will model fluid flow in the sub-domain region.
2) Don't use a subdomain and remove it from the mesh. Then apply the heat source as a boundary condition on the faces. This way you do not model the fluid flow in the sub-domain region.

Your choice.

Flaky October 7, 2010 07:51

Quote:

Originally Posted by ghorrocks (Post 278238)
You have two choices:

1) Model the sub-domain as a fluid region and apply the heat source as a volumetric heat source. This way you will model fluid flow in the sub-domain region.
2) Don't use a subdomain and remove it from the mesh. Then apply the heat source as a boundary condition on the faces. This way you do not model the fluid flow in the sub-domain region.

Your choice.

Hi ghorrocks,

Thanks for your reply.
Correct me if i have interpreted your advice wrongly.

The Domain being the Fluid and the sub-boundary created would be considered as boundaries on the Fluid itself. For Sub-domain created that would still be model as a fluid region. Thus for options one which u stated it would be a heat transfer from the fluid.

I am looking for a "fire" heat source region to transfer the heat to the fluid. Therefore currently my fire region which is a void as shown above only has surfaces sharing with the fluid region. So my choice has to be option 2?

ghorrocks October 7, 2010 08:10

If you have set the sub-domain as the same material as the main domain then the sub-domain is merely a region you can apply stuff to - in your case a volumetric heat source.

I have no idea what you final sentence means but the difference between my two options is whether you model the fluid flow in the sub-domain or not. Both methods will work fine.

Flaky October 7, 2010 08:33

Quote:

Originally Posted by ghorrocks (Post 278250)
If you have set the sub-domain as the same material as the main domain then the sub-domain is merely a region you can apply stuff to - in your case a volumetric heat source.

I have no idea what you final sentence means but the difference between my two options is whether you model the fluid flow in the sub-domain or not. Both methods will work fine.


Pardon my lack of explanation.

http://img227.imageshack.us/img227/3...oomincolor.png

The areas point by the blue lines are of the same material and they are the fluid region. The area circle in pink is the "void" area where the suppose "fire" should be.

For my case the area of my heat source is an empty space without any meshing. So i should be modeling the heat source as a boundary setting the surfaces circle in pink as the boundary conditions?

ghorrocks October 7, 2010 08:36

I see what you are doing now. In that case apply the heat source as a heat flux to those boundary faces.

Flaky October 7, 2010 08:40

Quote:

Originally Posted by ghorrocks (Post 278259)
I see what you are doing now. In that case apply the heat source as a heat flux to those boundary faces.

Thank you so much, you have been a great help. :D


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