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Fluent - Flow/heat transfer over porous media - possibly interface issue

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Old   March 3, 2018, 18:55
Default Fluent - Flow/heat transfer over porous media - possibly interface issue
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Sam
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Hey guys,

I am new to CFD, Fluent, and numerical methods in general.

I am simulating flow (laminar) and heat transfer over ( and through) a porous structure using Fluent. Just think of flow over a flat plate, but the plate surface is covered with a thickness of porous layer. The porous structure has low permeability, therefore the flow speed through the porous structure is very small. I have heat flux BC at the plate bottom wall and a mass flux BC for the flow.

----------------------------------------
Open Channel: Flow --->
----------------------------------------
Porous Wall: Flow --->
----------------------------------------
Solid Plate: No Flow
----------------------------------------

In my mind, I separated heat transfer into three parts:
  1. Convection at the plate wall (plate-porous interface)
  2. Interfacial convection (convection through the porous wall)
  3. Convection at the open flow - porous wall (porous-liquid interface)

I am using a 2D model. I am using non-equilibrium thermal model for the energy equation. At the moment, I am interested in the third item: convection at the porous-liquid interface. Thus, I set the interfacial convection coefficient to 0 W/m-K.

Problem: The Fluent model does not seem to capture the convection at the liquid/porous interface (3). The only convection seems to occur at the solid wall surface. Why do I think that? I decrease the porosity of the porous wall to 10% while keeping the permeability constant and the total thermal resistance between the flow and the solid wall increases. Plate-porous interface area is decreasing, but the porous-liquid interface is increasing. Thus, I would think the total thermal resistance should decrease, because (3) should dominate (1).

I did some research and stumbled upon this question: https://www.researchgate.net/post/Is..._in_the_domain

Possible Explanation: When I click on the "non-equilibrium model: option on Fluent, it automatically creates a solid zone and connects the porous liquid zone to this newly created zone. By looking at the answers in the link I provided, I think the newly created solid zone does not have any connection to the solid wall nor to the open flow. This might be why there is no convection at the porous/liquid interface???

Do you think this is the problem, if so how can I solve this?
Or do you think I am looking at the heat transfer the wrong way?

P.S. The flow distribution matches analytical correlations, I don't think anything is wrong with the flow model. I use ANSYS workbench for creating the mesh. I have no idea how to use Gambit or anything else.

Thank you for your time!
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convection, fluent, heat transfer, interface, porous

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