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cross-section averaged fluid temperature as a function of flow direction

Posted Nov 16, 2013, 12:46 a.m. EST Fluid & Heat, Heat Transfer & Phase Change 5 Replies

Kumar
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Hi,

I am modeling 3D laminar flow with heat transfer in a channel of rectangular cross-section.

How can I implement the attached formula for mean fluid temperature?

I would like to determine the mean fluid temperature at each cross-section as a function of the flow direction.

I am currently using T_mean = mod1.intop1(u*T)/intop1(mod1.u), which gives me the average temperature at the inlet cross-section (x=0), since intop1 is the integration over the inlet face.

The documentation mentions a function called linear projection but this appears to be for line integrals. I get an error when I use this function.

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5 Replies Last Post May 15, 2014, 11:40 a.m. EDT
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 1 decade ago Nov 16, 2013, 6:18 p.m. EST
If you just need the information for output and not to be used in the simulation itself, you can just use the cut plane feature of the results section of the model tree.

If you need the information within the model tree, you can create work planes within the model where you want to integrate the values. You can create variables and/or coupling variables to compute these quantities.

There are several ways you could do this.
If you just need the information for output and not to be used in the simulation itself, you can just use the cut plane feature of the results section of the model tree. If you need the information within the model tree, you can create work planes within the model where you want to integrate the values. You can create variables and/or coupling variables to compute these quantities. There are several ways you could do this.
Kumar
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Posted: 1 decade ago Nov 17, 2013, 11:13 p.m. EST
James,

Thanks for the response.

If I create work planes within the model, wouldn't the values be calculated only on these specific planes?

Can I get cross-sectionally averaged values as a continuous function of x?

James, Thanks for the response. If I create work planes within the model, wouldn't the values be calculated only on these specific planes? Can I get cross-sectionally averaged values as a continuous function of x?
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 1 decade ago Nov 18, 2013, 11:22 a.m. EST
That is the only way I know how to do it. This type of feature is something that needs to be incorporated into the model in a more user-friendly manner. You also might want to become familiar with coupling variables and then see if using this might also deliver the desired features.
That is the only way I know how to do it. This type of feature is something that needs to be incorporated into the model in a more user-friendly manner. You also might want to become familiar with coupling variables and then see if using this might also deliver the desired features.
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago Nov 18, 2013, 11:51 a.m. EST
Hello Kumar,
You can accomplish what you want using a general projection model coupling, see Reference Manual, version 4.3b, page 288. A basic example is attached: the Line Graph 1 node computes the integral of T as a function of x.
Best,
Jeff
Hello Kumar, You can accomplish what you want using a general projection model coupling, see Reference Manual, version 4.3b, page 288. A basic example is attached: the Line Graph 1 node computes the integral of T as a function of x. Best, Jeff
Panagiotis Giotakos
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Posted: 1 decade ago May 15, 2014, 11:40 a.m. EDT
Hi Jeff,

I am trying to use general projection in the same geometry as the example model you provided,(a simple rectangular pipe, laminar flow of water with free tetrahedral mesh) in order to plot the average velocity,(spf.U), (average in a yz cross-section) across the length of the pipe (x).
Thank you in advance for your help
Hi Jeff, I am trying to use general projection in the same geometry as the example model you provided,(a simple rectangular pipe, laminar flow of water with free tetrahedral mesh) in order to plot the average velocity,(spf.U), (average in a yz cross-section) across the length of the pipe (x). Thank you in advance for your help

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