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-   -   Average Nusselt number (http://www.cfd-online.com/Forums/openfoam-solving/98069-average-nusselt-number.html)

 Goutam March 2, 2012 07:15

Average Nusselt number

Dear Friends,

I have calculated local Nusselt number at the wall. How to calculate Average Nusselt number at the heated wall in OpenFOAM?

(I am cosidering a square cavity)

Can you help me?

 giovanni10 April 6, 2012 13:00

Quote:
 Originally Posted by Goutam (Post 347270) Dear Friends, I have calculated local Nusselt number at the wall. How to calculate Average Nusselt number at the heated wall in OpenFOAM? (I am cosidering a square cavity) Can you help me? Thanks for your time.
Dear Foamer,
Did you finally find a solution to your problem? Unfortunately, I`m not an expert in C++. So, It is too difficult for me. I would like to calculate the local and average Nusselt number in the same geometry as you[ I am working on a 2D laterally and volumetrically heated square cavity.] Could you help me? Thanks in advance!

 giovanni10 April 6, 2012 13:01

How did you calculate the local Nusselt number at the wall?

Quote:
 Originally Posted by Goutam (Post 347270) Dear Friends, I have calculated local Nusselt number at the wall. How to calculate Average Nusselt number at the heated wall in OpenFOAM? (I am cosidering a square cavity) Can you help me? Thanks for your time.
How did you calculate the local Nusselt number at the wall?

 Goutam April 7, 2012 16:02

See this link. This is the code for local Nusselt number calculation:

http://www.cfd-online.com/Forums/ope...lt-number.html

Thanks

Goutam

 Goutam April 7, 2012 16:09

Procedure of calculation of Average Nusselt number:

Three ways:

1) in your code, sum all your Nusselt number values for one patch (not all patches) times de area of each element; sum all areas of elements/cells of the same patch; divide the nusselt values sum by the area sum
2) in paraFoam, use filter "extractBlock" to extract the patch you want the average, use filter "integrate variables", it will open an spreadsheet, look for Area value in Cells or Points, look for Nusselt value in Cells or Points, divide Nusselt integrated value by the Area integrated value.
3) write this in the terminal: patchAverage localNusselt patchName

 dspiit August 29, 2012 04:17

How to calculate Average Nusselt number over the whole surface in COMSOL?

(I am cosidering a square cavity)

Can you help me?

 Goutam August 29, 2012 04:35

Quote:
 Originally Posted by dspiit (Post 379235) How to calculate Average Nusselt number over the whole surface in COMSOL? (I am cosidering a square cavity) Can you help me? Thanks in advance.
Yeah, I can help you. I did this before in Comsol. Why you will calculate the Avg Nu over the whole surface. You need to calculate this at the heated wall.

Consider the nondimensional expression for Nu. Say, Nu = Integrate ( dT/dx ) dx. Then chose the heated wall and write the expression Tx. It will give you average Nusselt number.

 dspiit September 2, 2012 17:33

Dear Gautam,

Could you please explain me the procedure how to do it, as you explained in your earlier post?

 ronin July 21, 2013 23:27

Quote:
 Originally Posted by Goutam (Post 379242) Yeah, I can help you. I did this before in Comsol. Why you will calculate the Avg Nu over the whole surface. You need to calculate this at the heated wall. Consider the nondimensional expression for Nu. Say, Nu = Integrate ( dT/dx ) dx. Then chose the heated wall and write the expression Tx. It will give you average Nusselt number.

This equation is applicable to a flat wall. How do I calculate the Nusselt number along a Circular surface in comsol?

Thanks

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