Data extract from faces

Gerrit · February 13, 2016, 10:46

Hi everyone,

I have a question concerning the evaluation of my simulation.
My case is a heat transfer simulation of a gas flowing over a heated wire in a pipe (I used buoyantSimpleFoam). I want to calculate the local Nusselt number and therefore I would like to have the heat flux and the surface area of the faces at the wire.

I already searched for answers, but the threads were already quite old.

Has anyone a hint for me how to do this or where to look?

Thank you!
Best

Gerrit · February 23, 2016, 08:43

Hi again,

after some research, Google and time I try to answer my own question:
about the heat transfered to the fluid: in postProcessing there is a tool called "wallHeatFlux" that might help.

Sadly I still did not found a way to gain the surface area of a face...

However I found an older thread to write a function based on wallGradU that returns a temperature Gradient at walls in normal direction:
http://www.cfd-online.com/Forums/ope...ient-wall.html

How does this help for the local Nusselt number? The local Nusselt number can be defined on an angle:

Nu_local= - L/(T - T_infinity) * dT/dn

where dT/dn is the temperature gradient in normal direction based on an angle (I have to refer to a cylinder so it makes sense to include an angle here).
A source for this definition can be found in the article "A correlation for the calculation of the local Nusselt number around circular cylinders in the range 10 <= Re <= 250 and 0.1 <= Pr <= 40"

Best

February 13, 2016, 10:46	Data extract from faces	#1
Gerrit Member Join Date: Jul 2015 Location: Aalborg Posts: 83 Rep Power: 10	Hi everyone, I have a question concerning the evaluation of my simulation. My case is a heat transfer simulation of a gas flowing over a heated wire in a pipe (I used buoyantSimpleFoam). I want to calculate the local Nusselt number and therefore I would like to have the heat flux and the surface area of the faces at the wire. I already searched for answers, but the threads were already quite old. Has anyone a hint for me how to do this or where to look? Thank you! Best

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February 23, 2016, 08:43		#2
Gerrit Member Join Date: Jul 2015 Location: Aalborg Posts: 83 Rep Power: 10	Hi again, after some research, Google and time I try to answer my own question: about the heat transfered to the fluid: in postProcessing there is a tool called "wallHeatFlux" that might help. Sadly I still did not found a way to gain the surface area of a face... However I found an older thread to write a function based on wallGradU that returns a temperature Gradient at walls in normal direction: http://www.cfd-online.com/Forums/ope...ient-wall.html How does this help for the local Nusselt number? The local Nusselt number can be defined on an angle: Nu_local= - L/(T - T_infinity) * dT/dn where dT/dn is the temperature gradient in normal direction based on an angle (I have to refer to a cylinder so it makes sense to include an angle here). A source for this definition can be found in the article "A correlation for the calculation of the local Nusselt number around circular cylinders in the range 10 <= Re <= 250 and 0.1 <= Pr <= 40" Best