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Valued Contributor
tfjield
Posts: 98
Registered: ‎06-19-2012

Wonky Uncoupled CFD/Thermal Results

134 Views, 2 Replies
09-13-2012 03:40 PM

Hey Guys,

 

I'm running an uncoupled CFD/thermal analysis to determine the effect of flowing water on the heat distribution.

 

I've created a very simple proof-of-concept model to verify the results, and I'm seeing some strangeness.

 

First, I created the thermal model and meshed it appropriately.  Then I copied the scenario and created a CFD model by suppressing the 3 non-fluid parts, applied the appropriate CFD boundary conditions, ran it, and got steady state results.

 

Then, back in the thermal model, I have applied the Fluid Convection results using the other scenario and have run the model.  It appears as if it's not applying the velocities right, as can be seen in the outputs below.

 

Here is the water slice mesh:

 

Water Mesh.png

 

Here are the results of the water flowing in steady state:

 

Water Flow.png

 

There is a fixed velocity on the left, which is why it's all green.  And here's a view of the output face:

 

Water Flow 2.png

 

So that all looks right to me.

 

Here's the thermal model:

 

Column Mesh.png

 

You can see the water layer inside of it.  There is a surface heat source between the bottom (white) and middle (pink) sections.  The top and bottom surfaces of the column are held at 0 degrees.

 

With no water flowing, the results look like this:

 

Flux Results No Flow.png

 

That's as I would expect.

 

However, with flow, the results look like this:

 

Flux Results.png  Flux Results 2.png

 

Any idea what could be going on here??  I can upload the model if the answer isn't obvious from the images above.

 

Thanks!

Current version of Mechanical & Multiphysics: 2013 SP2 (2013.02.00.0010 2-Oct-2012)
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Valued Contributor
tfjield
Posts: 98
Registered: ‎06-19-2012

Re: Wonky Uncoupled CFD/Thermal Results

09-25-2012 05:57 PM in reply to: tfjield

No one??

 

I'm stuck.  I have no idea what's going on.  I can't tell if this is a bug in Multiphysics or if I'm doing something wrong.

 

Right now, my conclusion is that uncoupled Multiphysics results cannot be trusted.  This simple model demonstrates a fundamental flaw.

 

Perhaps a coupled simulation would give accurate results?  I'm not sure, because the simulation won't finish...

 

I've attached the model, if anyone wants to jumps in.  (Need to remove .zip from the end of the .z01, .z02, and .z03 pieces before unzipping.)

 

Thanks,

Todd

 

 

Current version of Mechanical & Multiphysics: 2013 SP2 (2013.02.00.0010 2-Oct-2012)
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Valued Contributor
tfjield
Posts: 98
Registered: ‎06-19-2012

Re: Wonky Uncoupled CFD/Thermal Results

09-25-2012 05:58 PM in reply to: tfjield

Here's the last part of the zip file.  Remember to use the .zip from the .z03 file before unzipping.

Current version of Mechanical & Multiphysics: 2013 SP2 (2013.02.00.0010 2-Oct-2012)
Please use plain text.