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Defining porous media inside a domain

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Old   May 3, 2012, 02:14
Question Defining porous media inside a domain
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Soroush
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Hi guys,
Is it possible to define a sub-domain within our main flow domain and consider porosity only for that domain.
For example consider a cylinder in the flow, how can I define the cylinder in the flow to be porous? Can I still consider no-slip boundary condition (in direction tangent to the surface) for cylinder surface.

Lets give you a tangible example: assume that our cylinder is made of twisted coils, How can I simulate it in fluent?

Thanks for your help
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Old   May 3, 2012, 03:08
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You can create the spiral domain and define it/its surrounding as porous zone. But you cannot define no slip conditions as the porous zone is treated as fluid zone.
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Old   May 3, 2012, 03:10
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And for the cylindrical outer surface you can go with no slip boundary condition
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Old   May 3, 2012, 03:15
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Thanks for your answer Krishna,

I haven't simulated porous media before, so I didn't completely understand what you have said.
What do you mean by "Spiral domain"?
do you mean that I should define the volume inside the cylinder as porous domain and its surface as wall? Then how the fluid is supposed to enter the porous domain?
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Old   May 3, 2012, 09:00
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Hi Soroush
Your cylinder will be the porous domain. You don't need to model the spiral inside, but your resistance coefficients should be accurate to model it as a porous media. Alternately you could use a porous jump (2D plane) ONLY IF your resistance to flow is in the flow direction.

Your walls of the domain should be according to how the flow should enter. Those surfaces which allow flow are interiors and those that dont are walls.

Regards
Luke
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Old   May 3, 2012, 09:14
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Tahnks Luke,

So you're telling that the cylinder should be defined as porous domain and there is no need to define its boundaries (across the flow direction) separately?
Can resistance coefficients work to capture the real physic of the flow, I mean there should be a kind of no slip condition on the cylinder wall (although not like fully solid wall).

BTW, what is "spiral domain" any way?

Cheers,
>Soroush
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Old   May 7, 2012, 02:17
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The faces across the flow direction should be defined as interiors/interfaces.

Resistance can only capture the pressure drop and not the real flow physics since using the porous media model implies that you have simplified your geometry.

Spiral domain refers to the domain that contains the twisted coils you mentioned in your first post.

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Luke
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