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Airfoil Average Nusselt Number calculation

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Old   March 2, 2011, 23:46
Default Airfoil Average Nusselt Number calculation
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Hi everyone my current version of ANSYS Fluent is 12.1

The type of flow I am using is a Spalart Allarmaras Model

Please correct me if I am wrong

Now, I wantwant to calculate an average nusselt number from the Solution
so do I just simply click "monitor" -> " Surface Monitor"

Report Type: Integral
Field Variable: Wall Fluxes, Surface Nusselt Number??

and also how do I calculate the Reynolds number of the flow as well ?

Thanks =)
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Old   March 3, 2011, 01:25
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I have the Nusselt Number Distribution around the airfoil

does the Nu Distribution look like that ?



and how do I average them ? just add them all and divide by the number of point, n ???

ps: this airfoil is a unit length airfoil

Thanks
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Old   March 3, 2011, 03:41
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Hi,
before computing Nu No., be sure that your reference values are correct.(report->reference values)
I think for evaluating average Nu No., you can compute total heat transfer from airfoil and then obtain an equivalent h(heat transfer coefficient) and then compute Nu.(just a suggestion)
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Old   March 3, 2011, 04:47
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Quote:
Originally Posted by Amir View Post
Hi,
before computing Nu No., be sure that your reference values are correct.(report->reference values)
I think for evaluating average Nu No., you can compute total heat transfer from airfoil and then obtain an equivalent h(heat transfer coefficient) and then compute Nu.(just a suggestion)
Yes I've checked the reference value are the correct for air properties

as far as obtaining equivalent h from total heat transfer...
what delta temperature should I use ?? ( Temperature varies along the chord length too)

Thanks,
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Old   March 3, 2011, 05:21
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Quote:
Originally Posted by y2k_o__o View Post
Yes I've checked the reference value are the correct for air properties

as far as obtaining equivalent h from total heat transfer...
what delta temperature should I use ?? ( Temperature varies along the chord length too)

Thanks,
I think it's a good idea to use dT=(Tave-Tinf). you can obtain Tave from report->surface integral->average facet. isn't it?
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Old   March 3, 2011, 06:45
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Quote:
Originally Posted by Amir View Post
I think it's a good idea to use dT=(Tave-Tinf). you can obtain Tave from report->surface integral->average facet. isn't it?
so what you're saying is:

h_avg = overall_heat_transfer_rate / ( T_avg - T_fluid )

Nu_avg = h_avg * chord_length / k_fluid

correct me if I am wrong
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Old   March 3, 2011, 08:37
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Quote:
Originally Posted by y2k_o__o View Post
so what you're saying is:

h_avg = overall_heat_transfer_rate / ( T_avg - T_fluid )

Nu_avg = h_avg * chord_length / k_fluid

correct me if I am wrong
yes, it's right if T_fluid & k_fluid remain constant during solution.
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