# Average Nusselt number

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 March 2, 2012, 06:15 Average Nusselt number #1 Senior Member   Goutam Saha Join Date: Dec 2011 Location: UK Posts: 131 Rep Power: 14 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.

April 6, 2012, 13:00
#2
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giovanni silva
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Quote:
 Originally Posted by Goutam 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!

April 6, 2012, 13:01
How did you calculate the local Nusselt number at the wall?
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giovanni silva
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Quote:
 Originally Posted by Goutam 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?

 April 7, 2012, 16:02 #4 Senior Member   Goutam Saha Join Date: Dec 2011 Location: UK Posts: 131 Rep Power: 14 See this link. This is the code for local Nusselt number calculation: http://www.cfd-online.com/Forums/ope...lt-number.html Thanks Goutam

 April 7, 2012, 16:09 #5 Senior Member   Goutam Saha Join Date: Dec 2011 Location: UK Posts: 131 Rep Power: 14 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

 August 29, 2012, 04:17 #6 New Member   DPAN Join Date: Aug 2012 Posts: 2 Rep Power: 0 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.

August 29, 2012, 04:35
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Goutam Saha
Join Date: Dec 2011
Location: UK
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Quote:
 Originally Posted by dspiit 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.

 September 2, 2012, 17:33 #8 New Member   DPAN Join Date: Aug 2012 Posts: 2 Rep Power: 0 Dear Gautam, Could you please explain me the procedure how to do it, as you explained in your earlier post?

July 21, 2013, 23:27
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M J Alam Khan
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Quote:
 Originally Posted by Goutam 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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