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November 21, 2012, 12:05 
about Nusselt number: local or average?

#1 
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amine
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hi every one,
wanna ask u how to find nusselt average and also nusselt local and how to plot them using fluent 6.3 quickly please thank you so much 

November 22, 2012, 08:21 

#2 
New Member

For local Nusselt Number
Plot > XY Plot > Wall Fluxes... > Surface Nusselt Number... Select the surface where you want to obtain the local Nusselt number... You can save the data file or see directly in FLUENT window... For Average Nusselt Number: Report > Surface Integrals > Report Type > Facet Average > Field Variable (Wall Fluxes) > Surface Nusselt Number.... Again select the surface where you want to obtain the average Nusselt number... 

November 22, 2012, 16:47 

#3  
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amine
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Quote:


November 22, 2012, 17:56 

#4 
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amine
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for the local nusselt it gave me a graph not a value!how to plot it plz : x direction or y direction?curves or ...?
for the average the average nusselt i got is bigger than nusselt average found in litterature : i am simulating laminar natural convection through an enclosure with partially active wall!!!where's the problem plz tell me ,or give me some steps to simulate this problem from prepossesing to postprossesing thnk u so much 

November 23, 2012, 08:22 

#5  
New Member

Quote:
Rather than plotting the local Nusselt number, you can chose to write in a file and see the values you are interested in. Average Nusselt number is simply the integration of local values over the selected surface. Please check the boundary conditions are suitably defined on all the surface... 

November 23, 2012, 13:56 

#6  
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amine
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Quote:
i have Ra=10^3 ~ 10^6 results,in order to compare them in one graph to see the differences how to do that plz ,iam new in cfd plz help me 

November 23, 2012, 15:57 

#7  
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amine
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Quote:
i have a question in simulation of natural convection through square cavity i obtained Nu average value is 1.289206 for Rayleigh number 10^3!!!in the litterature the Nu average value is 1.118 why?where is the mitakes may be i did???plz if u have a short and brief tutorial could u give me step by step plz from gambit 2.0 to solving on fluent 6.3,i am working for this problem for 2 weeks but i cant got it ,,,i am so tired thank u ramp for all 

November 27, 2012, 07:55 

#8  
New Member

Quote:
Save the local Nusselt number data for all values of Ra in separate files... Open these files in MS Excel and then combine all the data in one file to plot them on a single graph... 

November 27, 2012, 07:57 

#9  
New Member

Quote:
Are you using the similar numerics (mesh size and numerical schemes, etc.) to that used in the literature? You may try refining the mesh and see the results... 

November 27, 2012, 10:14 
i am using 120x120

#10  
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amine
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Quote:
i tried : 31x31 41x41 52x52 60x60 80x80 90x90 100x100 110x110 120x120 130x130 161x161 but my results were not good please Ramp could u help me out?i am really lost could u teach me the tutorial ste[ by step?or tell me the mistakes i did,here are the steps i ve done: Gambit2.2: create surface(1x1 m^2)/mesh: create boundray layer /mesh edges biexponent 0.6 and number count 120 for all /mesh surface/define boundary wall/and continum fluid/export .msh and save fluent 6.3 : read case/chek/size/scale/display grid define: solverenrgyviscous/materials/operating conditions Ra=1e+04/boundary conditions solve:control solutioninitializeresidualsiterate for compute the Nu average number at y/2 i did: report/integral surface/facet average/wall flux/surface nusselt number/select heated wall/compute but my result is not good ,i tried many times plz tell me how to do all that(postprocessing) as : at y/2: Nu local and average;velocities;temperature... thank u so much 

November 27, 2012, 10:23 

#11  
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amine
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Quote:
sorry Ramp : at x/2 not y/2 thnks 

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