CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   Airfoil Average Nusselt Number calculation (http://www.cfd-online.com/Forums/fluent/85631-airfoil-average-nusselt-number-calculation.html)

 y2k_o__o March 2, 2011 23:46

Airfoil Average Nusselt Number calculation

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 =)

 y2k_o__o March 3, 2011 01:25

I have the Nusselt Number Distribution around the airfoil

does the Nu Distribution look like that ?

http://i40.photobucket.com/albums/e2...lotgrid100.jpg

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

 Amir March 3, 2011 03:41

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)

 y2k_o__o March 3, 2011 04:47

Quote:
 Originally Posted by Amir (Post 297730) 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,

 Amir March 3, 2011 05:21

Quote:
 Originally Posted by y2k_o__o (Post 297739) 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?

 y2k_o__o March 3, 2011 06:45

Quote:
 Originally Posted by Amir (Post 297750) 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

 Amir March 3, 2011 08:37

Quote:
 Originally Posted by y2k_o__o (Post 297768) 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.

 All times are GMT -4. The time now is 02:31.