How to assign thermal conductivity at interface between fluid and porous region

Goenitz · June 3, 2019, 09:44

I have thermal conductivity of material (metal foam=porous), inlet condition and wall condition. How can I assign that thermal conductivity of porous region at interface of porous-fluid region for heat transfer. (green region is interface:Fluid left, Porous right). I have neither temperature at interface, nor heat transfer coefficient nor heat flux.

Opaque · June 3, 2019, 12:50

Confused.

You have materials on both sides of the interface, and their thermal conductivities specified for them, correct?

Why would you need another thermal conductivity at the interface?

Goenitz · June 4, 2019, 15:17

Yes, I have Aluminium on one side and air on the other. They both take default thermal conductivity value. In literature, I have nothing but thermal conductivity of Al foam (porous). So as a boundary condition, I need to define thermal conductivity of interface, if possible. CFX, as shown in pic, takes either solid interface value as either adiabatic or heat transfer coefficient or as flux. So I posted the question to see if that possible. If not how to overcome this.

Goenitz · June 5, 2019, 08:29

Anyway, there is no option in CFX for fluid-porous interface. There is for Solid-Porous interface. At that interface just to go the GGI interface and enable "Additional Model" for the heat transfer. Here you will be asked to provide some information to formulate the resistance.

As interface is thin region, so I can assume it to be adiabatic.

ghorrocks · June 5, 2019, 19:23

You don't need interfaces between a fluid region and a porous region. The porous region is just subdomains inside a fluid domain. It is one domain, so no interfaces are required.

Goenitz · June 6, 2019, 12:20

Quote:

Originally Posted by ghorrocks

You don't need interfaces between a fluid region and a porous region. The porous region is just subdomains inside a fluid domain. It is one domain, so no interfaces are required.

Actually in Sub-Domian we can assign sources in CFX. However, for every domain we have to create separate blocks and then assign it respective domain e.g.solid, porous, fluid etc.

Another Q is which I made a thread before how to assign a normal boundary condition to wall in CFX?

ghorrocks · June 6, 2019, 18:35

You can also define a subdomain to have a porous loss function in the source terms.

So make the porous regions subdomains and then you don't have any interfaces to worry about.

June 5, 2019, 19:23		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You don't need interfaces between a fluid region and a porous region. The porous region is just subdomains inside a fluid domain. It is one domain, so no interfaces are required. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

June 6, 2019, 18:35		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You can also define a subdomain to have a porous loss function in the source terms. So make the porous regions subdomains and then you don't have any interfaces to worry about. Goenitz likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 3, 2019, 12:50		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,804 Rep Power: 32	Confused. You have materials on both sides of the interface, and their thermal conductivities specified for them, correct? Why would you need another thermal conductivity at the interface?

June 4, 2019, 15:17		#3
Goenitz Member Abdullah Arslan Join Date: Apr 2019 Posts: 94 Rep Power: 7	Yes, I have Aluminium on one side and air on the other. They both take default thermal conductivity value. In literature, I have nothing but thermal conductivity of Al foam (porous). So as a boundary condition, I need to define thermal conductivity of interface, if possible. CFX, as shown in pic, takes either solid interface value as either adiabatic or heat transfer coefficient or as flux. So I posted the question to see if that possible. If not how to overcome this.

June 5, 2019, 08:29		#4
Goenitz Member Abdullah Arslan Join Date: Apr 2019 Posts: 94 Rep Power: 7	Anyway, there is no option in CFX for fluid-porous interface. There is for Solid-Porous interface. At that interface just to go the GGI interface and enable "Additional Model" for the heat transfer. Here you will be asked to provide some information to formulate the resistance. As interface is thin region, so I can assume it to be adiabatic.