Nusselt Number problem
(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. 695719, 1994. 
I have calculated the local one.

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 
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By the way, what Ra and Pr have you studied (modelled)? Because I have quite some problems with the RayleighBenard 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 http://www.cfdonline.com/Forums/ope...implefoam.html ) Is there a chance that you send me your case files? Best, primoz 
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I would realy appreciate if you could send me your natural convection case (i.e. files)! I still have some problems with the RayleighBenard 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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