Fluent Custom Field function

saidkhaled · March 28, 2020, 09:46

Dear all,
I hope all of u are doing well ,
I am solving natural convection inside heated cavity and i would like to calculate some quantities using custom field function. However as may be seen below the results are wrong and unfortunately this is the case for all mathematical operations. my question is do u have guys an idea how to solve this problem. thank you so muchcustom field function temperature.jpg

vinerm · March 28, 2020, 16:20

The reason for that is volume averaging. If all the cells in your mesh are of exactly same volume, then answer would be what you expect, i.e., 90000. However, that is certainly not the case. Volume averaged temperature is defined as

$\frac{\sum T_{cell} \times V_{cell}}{\sum V_{cell}}$

vinerm · March 30, 2020, 07:16

The solution is to report out the temperature values for the cell. Go to File > Export > Solution data and then report temperature values for all cells in a text file. Then you can load this file in a text editor, such as vi or textpad to look at how much variation is there in temperature values.

March 28, 2020, 09:46	Fluent Custom Field function	#1
saidkhaled New Member said khaled Join Date: Jan 2019 Posts: 3 Rep Power: 7	Dear all, I hope all of u are doing well , I am solving natural convection inside heated cavity and i would like to calculate some quantities using custom field function. However as may be seen below the results are wrong and unfortunately this is the case for all mathematical operations. my question is do u have guys an idea how to solve this problem. thank you so muchcustom field function temperature.jpg

March 28, 2020, 16:20	Volume Average	#2
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36	The reason for that is volume averaging. If all the cells in your mesh are of exactly same volume, then answer would be what you expect, i.e., 90000. However, that is certainly not the case. Volume averaged temperature is defined as $\frac{\sum T_{cell} \times V_{cell}}{\sum V_{cell}}$ Sai Krishna and saidkhaled like this. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

March 30, 2020, 07:16	Exact Solution	#3
vinerm Senior Member Vinerm Join Date: Jun 2009 Location: Nederland Posts: 2,946 Blog Entries: 1 Rep Power: 36	The solution is to report out the temperature values for the cell. Go to File > Export > Solution data and then report temperature values for all cells in a text file. Then you can load this file in a text editor, such as vi or textpad to look at how much variation is there in temperature values. Bibill likes this. __________________ Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.

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