# Why doesn't my simulation solve two energy equation?

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 April 8, 2019, 08:32 Why doesn't my simulation solve two energy equation? #1 Senior Member   Join Date: Sep 2017 Posts: 130 Rep Power: 7 Guys, I'm trying to simulate heat transfer in a conical body which is under cooling using a helical channel that water is throughing in it. here is two screenshoot of the body: The point is that Fluent doesn't solve two energy equation(energy equation for our fluid and solid). In fact it solve one energy equation and it doesn't converge properly. Here is a screenshot of the residuals: Here is a screenshot of the equations in Fluent Methinks that Fluent cannot recognize the existens of the solid body although the two body are avalible in Fluent, see Questions: How to make sure that Fluent is solving the both equations or just one equation? Is the above screenshot enough to know that Fluent is solving just one equation? If Fluent is solving just one equation, how to make it to solve the both energy equation? why Fluent don't recognize the both body? Do you any other problem? any other idea? Totally how to fix the problem?

 April 8, 2019, 09:05 #2 Senior Member   Moritz Kuhn Join Date: Apr 2010 Location: Germany, Dresden Posts: 171 Rep Power: 15 You are sure that your solid domain is well connected to your fluid domain, that meas a heat flow is possible?

April 8, 2019, 09:17
#3
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Quote:
 Originally Posted by MKuhn You are sure that your solid domain is well connected to your fluid domain, that meas a heat flow is possible?
No, I'm not sure. How can I check it?

Forgot to say that this is first time that I'm doing a heat-transfer project between a solid and a fluid.

 April 8, 2019, 09:31 #4 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,252 Rep Power: 63 Can't see pictures but... There is only one energy equation. Make sure you have proper connecting boundaries (interfaces!) between your fluid and solids.

April 8, 2019, 09:32
#5
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Moritz Kuhn
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For two-sided internal walls, the coupled boundary treatment between solid and fluid is always applied to wall and wall-shadow pairs. So under your boundary condtions you have to have something named with "shadow". If not, you can achive it under the thermal setup up of the face between your bodies and choose "coupled"
Attached Images

 April 8, 2019, 21:33 #6 Senior Member   Alexander Join Date: Apr 2013 Posts: 2,259 Rep Power: 33 I recommend you to delete contact surfaces in design modeler and remesh your model, so you will get conformal mesh. Looks like your problem comes from bad mesh best regards

 April 9, 2019, 16:24 #7 Member   Andrea Join Date: Mar 2018 Posts: 62 Rep Power: 7 Just plot heat flux and se if is 0 at the interface. If the mesh is not connected the flux will be 0

 April 9, 2019, 17:07 #8 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,252 Rep Power: 63 I can see the pictures now! But we are being bamboozled! Equations doesn't show energy equation at all! But your residuals plot clearly shows an energy residual. Stop trolling.

April 11, 2019, 06:41
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Sorry guys for delay and thank you for your replies

Quote:
 Originally Posted by LuckyTran ...There is only one energy equation...
But we have to different body, a solid and a fluidic body and due to this file:

http://www.afs.enea.it/fluent/Public.../PDF/chp11.pdf

We have two energy equation. Please pages 2 and 6
One for fluid and one for solid
So Fluent should solve two energy equation. Isn't it correct?

Quote:
 Originally Posted by LuckyTran ...Make sure you have proper connecting boundaries (interfaces!) between your fluid and solids.
Always when I open the project, I get these notations(4 notations):

Can you see the image?

I don't know if these notations could be related to my problem.

Quote:
 Originally Posted by MKuhn For two-sided internal walls, the coupled boundary treatment between solid and fluid is always applied to wall and wall-shadow pairs. So under your boundary condtions you have to have something named with "shadow". If not, you can achive it under the thermal setup up of the face between your bodies and choose "coupled"
I have just one shadow wall and it is coupled to its wall. I'm thinking that maybe the problem is in "Mesh Interfaces". Here is the images of cantact regions and "Mesh Interfaces" setting:

Do you see any problem?
Quote:
 Originally Posted by AlexanderZ I recommend you to delete contact surfaces in design modeler and remesh your model, so you will get conformal mesh. Looks like your problem comes from bad mesh best regards
Can I create two zone without contact surfaces? you can download my .agdb file from here:

Quote:
 Originally Posted by Andrea159357 Just plot heat flux and se if is 0 at the interface. If the mesh is not connected the flux will be 0
Just watched contours of "Surface heat transfer coef." for two cantact region. No doubtful point is seen. the legend was also ranged.

Quote:
 Originally Posted by LuckyTran I can see the pictures now! But we are being bamboozled!...
No joking, no bamboozling, no kidding,...
I have enough problem to attend. No time for kidding.

Quote:
 Originally Posted by LuckyTran Equations doesn't show energy equation at all! But your residuals plot clearly shows an energy residual. Stop trolling.
Interesting point. didn't realized that.
The Case & Data files are around 15MB. Would you like to see it? I can upload them somewhere to get it.

April 11, 2019, 13:00
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Lucky
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I'll just tell you even though you don't believe me that once you get Fluent set up properly and everything is working, you will find only one energy residual. There are lots of different forms of the energy equation and different ways to write it down, but there is only one principle of energy conservation. If you look closely you'll notice the energy equation in a solid is just a special case of the energy equation of a fluid.

Quote:
 Originally Posted by Roh I have just one shadow wall and it is coupled to its wall. I'm thinking that maybe the problem is in "Mesh Interfaces". Here is the images of cantact regions and "Mesh Interfaces" setting:
Both the wall and the shadow wall should have the coupled thermal boundary condition.

Quote:
 Originally Posted by Roh Just watched contours of "Surface heat transfer coef." for two cantact region. No doubtful point is seen. the legend was also ranged.

The point of someone telling you to check the heat flux is to check that the heat flux is not zero. So you have a non-zero heat transfer coefficient? Then there is heat transfer from solid to fluid and everything is working.

April 11, 2019, 13:53
#11
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Quote:
 Originally Posted by LuckyTran ... everything is working.
Yeah it looks but not properly.

• In "Equations" I cannot see energy equation as you saw in the images.
• The energy equation residual does not decrease to below e-03
• The solution didn't convege and oscillates severely (I've try to solve it as steady or transient but in both, the solution oscillated)
The problem is that I cannot find the problem!

 April 11, 2019, 22:23 #12 Senior Member   Alexander Join Date: Apr 2013 Posts: 2,259 Rep Power: 33 in my opinion the problem is your mesh (poor quality and interfaces) best regards

April 18, 2019, 11:33
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Quote:
 Originally Posted by AlexanderZ in my opinion the problem is your mesh (poor quality and interfaces) best regards

How can I make sure that the problem is because of mesh quality or interfaces?

For example when I do a "mesh check" for this project, I get this report:

Code:
``` Domain Extents:    x-coordinate: min (m) = -1.375240e+01, max (m) = -1.369300e+01
y-coordinate: min (m) = -1.648760e-02, max (m) = 1.649027e-02
z-coordinate: min (m) = -1.648960e-02, max (m) = 1.648955e-02
Volume statistics:
minimum volume (m3): 4.396650e-14
maximum volume (m3): 2.868624e-10
total volume (m3): 1.178235e-05
Face area statistics:
minimum face area (m2): 3.506865e-10
maximum face area (m2): 9.237542e-07
Checking mesh............................
Warning: Found 6 left-handed faces on sliding interface zone 6.
Mesh interface check failed!

Done.

WARNING: Mesh check failed.

To get more detailed information about the mesh check failure
increase the mesh check verbosity via the TUI command
/mesh/check-verbosity.```

It says that mesh interface check has failed. What could it mean?

Why is it a warning?

Why it's not an error?

How could I figure out this failure?

I've tried to use all of the commands in the sub-branch of "/mesh/repair-improve" to repair or improve the mesh but no progress has gained, so far!

Any other idea?

Edit: Here is some links to the similar problem:

Mesh check failed

https://studentcommunity.ansys.com/t...-check-failed/