# Nusselt Number problem

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 February 28, 2012, 14:33 Nusselt Number problem #1 Senior Member   Goutam Saha Join Date: Dec 2011 Location: UK Posts: 128 Rep Power: 5 (buoyantBousseinsqSimpleFoam) I want to calculate local and average Nusselt number for a square cavity when T_left=303 K, T_right= 283 K, T_ref= 293 K, Detta T = 20, u=v=0 for all wall and uper and lower wall are adiabetic. local Nu = -0.05 * Grad(T) at the wall average Nu = Integration [local Nu, {y, 0, 1}] How I will calculate this, please help me? I am considering the benchmark problem, paper name: Natural convection flow in a square cavity revisited: laminar and turbulent models with wall functions, International journal for numerical methods in fluids, vol. 18, pp. 695-719, 1994.

 March 3, 2012, 09:34 #2 Senior Member   Goutam Saha Join Date: Dec 2011 Location: UK Posts: 128 Rep Power: 5 I have calculated the local one.

 July 3, 2012, 09:10 #3 Member   Primoz Ternik Join Date: Apr 2009 Location: Maribor, Slovenia Posts: 65 Rep Power: 8 For obtaining the "average" Nusselt number use the numerical integration (Simpson's 1/3 method)! What version of Open Foam have you used for your calculation? Best, Primoz

July 5, 2012, 12:10
#4
Senior Member

Goutam Saha
Join Date: Dec 2011
Location: UK
Posts: 128
Rep Power: 5
Quote:
 Originally Posted by ternik For obtaining the "average" Nusselt number use the numerical integration (Simpson's 1/3 method)! What version of Open Foam have you used for your calculation? Best, Primoz
I have calculated both the local and average Nu. I am using OF 2.1.0.

July 5, 2012, 15:21
#5
Member

Primoz Ternik
Join Date: Apr 2009
Location: Maribor, Slovenia
Posts: 65
Rep Power: 8
Quote:
 Originally Posted by Goutam I have calculated both the local and average Nu. I am using OF 2.1.0.
Nice! I hope your results are in agreement with the benchmark!

By the way, what Ra and Pr have you studied (modelled)? Because I have quite some problems with the Rayleigh-Benard convection (laminar natural convection in a square cavity heated from bellow) for Pr=10 and Ra=1e05; I am using buoyantBoussinesqSimpleFoam (Open Foam 2.1.1) and results are "not good" (maybe you can check my post buoyantBoussinesqSimpleFoam )

Is there a chance that you send me your case files?

Best,
primoz

July 12, 2012, 05:14
#6
Member

Primoz Ternik
Join Date: Apr 2009
Location: Maribor, Slovenia
Posts: 65
Rep Power: 8
Quote:
 Originally Posted by Goutam I have calculated both the local and average Nu. I am using OF 2.1.0.
Dear Goutam,

I would realy appreciate if you could send me your natural convection case (i.e. files)!

I still have some problems with the Rayleigh-Benard convection (laminar natural convection in a square cavity heated from bellow) for Pr=10 and Ra=1e05; I am using buoyantBoussinesqSimpleFoam (Open Foam 2.1.1) and results are "not good".

Best,
Primoz

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