Entropy Calculations with Fluent
 

Hello,May you have a nice Day a head.

I am new user of Fluent Coding and UDf programming and i need your help for my case.May be my case is simple for you guys so kindly help me out and give me urgent help i will be very thankful to you guys.

My problem is that I need to find Entropy due to heat and Friction seperatly by the equations which i have attached over a flate plate having 3d domain.
As i have done a lot of research on this and uptill now i got an idea that it can be found with custom field function of Fluent by writing an equation in it.But i am not able to write that equation plus i also need to know how to get temperature gradients values that will be further used in the custom field function?

Kindly Help me Briefly i am really thankful to you guys for help.

Attachment 40962

dear Mohib Khan,
you can easily write these equation using fluent/define/custom field functions.
to access to temperature gradients:
in fluent command window 1-press enter 2- type solve 3-press enter
4-type set.5-press enter. Then select yes to all questions.
note that to access temperature gradients you must run your problem at least 1 iteration.
:)

Hello Hadii,
Thanks a lot for your response and your step by step procedure.
Can you please explain me one further thing that in order to find the entropy generation rate we need to apply this to surface integral or volume integral?And can this equation can find the entropy generation rate of fluid domain or it will give me the entropy generation rate of solid surface?
Thanks a lot once again for your help.
Mohib Khan

reply
 

hello my friend
You can see the units of entropy generation are W/(m3.K).
therefore, you should compute volume integrals of your custom field function using: report/volume integrals/volume integral
in cell zones you able to choose fluid or solid(if exists) and then click on compute.
have a good times

user defined function
 

Hello Mohib Anwar,
from your experience do you know how to write in user define function (1/density n x ∇p) or pressure gradient
where n is the unit vector of the outside normal