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Flow through the box filled with stones - porous?

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Old   July 27, 2010, 04:03
Default Flow through the box filled with stones - porous?
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Lukasz
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Hi all,
I noticed the problem which one I had missed when I was studying ansys documentation.
Assume that we have to model the flow through volume occupied with the stones, bricks, grains - no matter the size, this is bed filled with 3D objects. These objects produces pressure loss to the flow, of course.
Natural soultion is using porous domain, but this is a way of modelling a head losses. But what with a properties of the solid material itself? In my situation the problem is with heating these stones with hot air flow. Since there is no possibility of definition porous domain as a "solid-fluid" domain i was thinking about some trick with these objects heating fe. heat sink or something but up to the time have no idea.

Can somebody help?
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Old   July 27, 2010, 05:54
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Subhasish Mitra
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Finding out pressure drop in such cases is invariably through "porous media" concept which uses "Ergun" equation to find out pressure drop and this needs solid properties like porosity, particle dia etc as well.

You can define all those stones as a separate zone in GAMBIT and turn on the porous option in Fluent.
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Old   July 27, 2010, 06:54
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Yes, I agree that influence of the solid (this grains) on flow can be simulated using porosity models. But my problem is, that I want to model heating up this porous medium by hot air, and as far as I know ansys cfx not allowing to do this directly.
I was thinking about possibility of simulation of the very slow crossflow of very large number of particles (to simulate steady bed of stones) but unsure of results.

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Old   July 27, 2010, 07:19
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Glenn Horrocks
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I think this is a new feature in CFX V13. Try downloading the preview from the CFX community and give it a go.
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Old   July 27, 2010, 11:04
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Hi Glenn: unfortunately this time using version other than 10/11 is not possible,since I have to present input (which at least tryes to solve that problem).
There were two ideas on my mind:
- Euler-Euler flow - I wanted to add a very small velocity cross flow of bricks with appropiate packing. Seems to work but not very well - package can be higher than 100% what blocks the airflow. Can somebody help how to set up a constant package in the volume? Assume that volume fractions are know (entire volume is filled with bricks of constant shape) and I want only a fluid flow of the air passing between bricks and heat flow in the solid?
- I wanted to alter heat transfer coeff of the air in the volume occupied by solid. Not good idea but I want only roughly estimate heat diffusion.

Heeelp))

Luk
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Old   July 28, 2010, 07:52
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If you insist on doing it in an old version of the software I would use an additional variable for the porous material temperature and link it to the flow with a source term.
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