How is the heat transfer calculated with slip wall condition?

Meng Kong · December 3, 2015, 14:37

I am simulating indoor room environment using STAR-CCM+ and trying to use slip wall on the far-field wall. But I don't know how the heat transfer is calculated with slip wall condition. Can anybody help me with it? Many thanks.

FMDenaro · December 3, 2015, 15:03

Quote:

Originally Posted by Meng Kong

I am simulating indoor room environment using STAR-CCM+ and trying to use slip wall on the far-field wall. But I don't know how the heat transfer is calculated with slip wall condition. Can anybody help me with it? Many thanks.

what do you mean? if the slip condition is consequent to the assumption of inviscid condition, accordingly you have no conducibility in the fluid

Meng Kong · December 3, 2015, 16:18

Hi Filippo,
Thanks a lot for your help. By meaning slip-wall condition, I mean the velocity close to the wall is not zero. And in this case, my question is how the heat flux between the wall and air is calculated. What do you mean by "no conducibility"?
Meng

FMDenaro · December 3, 2015, 16:31

Quote:

Originally Posted by Meng Kong

Hi Filippo,
Thanks a lot for your help. By meaning slip-wall condition, I mean the velocity close to the wall is not zero. And in this case, my question is how the heat flux between the wall and air is calculated. What do you mean by "no conducibility"?
Meng

if the tangential velocity at the wall is not zero then you are assuming the no-viscosity hypothesis...
Working with such model drives to the Euler equations and the no-viscosity assumption for the momentum equation is completed in the energy equation by the absence of heat flux (q = - k Grad T = 0) due to the assumption k=0 everywhere in the fluid.

Meng Kong · December 3, 2015, 16:38

Hi Filippo,
I'm trying to understand your explanation. But if the heat conduction in the fluid is zero, there will be no heat transfer between the wall and air. Am I right? Many thanks.
Meng

FMDenaro · December 3, 2015, 16:51

Yes. The assumption for the Euler equation are indeed zero viscosity and zero thermal conductivity.

The first one set no viscous stress the second no heat flux

Meng Kong · December 3, 2015, 17:00

But in my case, I only use "slip-wall" condition on the far-field walls. All the other walls are set as "non-slip wall". And I also checked the results, it turned out that the heat transfer through the air is not zero. Many thanks.

FMDenaro · December 3, 2015, 17:15

Quote:

Originally Posted by Meng Kong

But in my case, I only use "slip-wall" condition on the far-field walls. All the other walls are set as "non-slip wall". And I also checked the results, it turned out that the heat transfer through the air is not zero. Many thanks.

ok, when you consider viscous conditions, then you cna simply set the condition of balance between heat flux in air (Fourier law) and heat transmission in the wall:

h (T- Tp) = - k Grad T

Meng Kong · December 3, 2015, 17:21

I may not have explained my question clearly. Actually I did not simulate the heat conduction in the wall. I'm only simulating the fluid field with constant wall temperature and slip-wall condition. I know when we are using non-slip wall condition, the convective heat transfer is calculated according to the boundary layer theory and wall function. But if the wall is set as "slip wall". I do not know how the convective heat transfer is calculated. I hope my explanation makes my question more clear. Many thanks.

flotus1 · December 3, 2015, 19:50

For an artificial boundary far away from the region of interest, a symmetry boundary condition is the appropriate choice. For the energy equation this implies that the heat flux normal to the boundary is zero.

The options you have when using a slip wall instead of a symmetry boundary condition depend on the program you are using. We have a CCM+ sub-forum here.

December 3, 2015, 14:37	How is the heat transfer calculated with slip wall condition?	#1
Meng Kong New Member NY Join Date: Dec 2015 Posts: 6 Rep Power: 10	I am simulating indoor room environment using STAR-CCM+ and trying to use slip wall on the far-field wall. But I don't know how the heat transfer is calculated with slip wall condition. Can anybody help me with it? Many thanks.

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December 3, 2015, 16:18		#3
Meng Kong New Member NY Join Date: Dec 2015 Posts: 6 Rep Power: 10	Hi Filippo, Thanks a lot for your help. By meaning slip-wall condition, I mean the velocity close to the wall is not zero. And in this case, my question is how the heat flux between the wall and air is calculated. What do you mean by "no conducibility"? Meng

December 3, 2015, 16:38		#5
Meng Kong New Member NY Join Date: Dec 2015 Posts: 6 Rep Power: 10	Hi Filippo, I'm trying to understand your explanation. But if the heat conduction in the fluid is zero, there will be no heat transfer between the wall and air. Am I right? Many thanks. Meng

December 3, 2015, 16:51		#6
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,849 Rep Power: 73	Yes. The assumption for the Euler equation are indeed zero viscosity and zero thermal conductivity. The first one set no viscous stress the second no heat flux

December 3, 2015, 17:00		#7
Meng Kong New Member NY Join Date: Dec 2015 Posts: 6 Rep Power: 10	But in my case, I only use "slip-wall" condition on the far-field walls. All the other walls are set as "non-slip wall". And I also checked the results, it turned out that the heat transfer through the air is not zero. Many thanks.

December 3, 2015, 17:21		#9
Meng Kong New Member NY Join Date: Dec 2015 Posts: 6 Rep Power: 10	I may not have explained my question clearly. Actually I did not simulate the heat conduction in the wall. I'm only simulating the fluid field with constant wall temperature and slip-wall condition. I know when we are using non-slip wall condition, the convective heat transfer is calculated according to the boundary layer theory and wall function. But if the wall is set as "slip wall". I do not know how the convective heat transfer is calculated. I hope my explanation makes my question more clear. Many thanks.

December 3, 2015, 19:50		#10
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,427 Rep Power: 49	For an artificial boundary far away from the region of interest, a symmetry boundary condition is the appropriate choice. For the energy equation this implies that the heat flux normal to the boundary is zero. The options you have when using a slip wall instead of a symmetry boundary condition depend on the program you are using. We have a CCM+ sub-forum here.