Fluent value vs UDF value discrepancy

argeus · May 27, 2011, 13:12

hello hello,
Any help highly appreciated.. please..

Im using a F_FLUX(t,tf) to extract data (mass flow rate) from fluent to a .txt file. x = F_FLUX (t,tf) access data from each elementary face. then I use a auxilliary variable, which sums the values from all elementary cells. looks like: y =+ x;. Now I have a total mass flow rate [kg/s] through a boundary face. But, when i try to compare this value with value accessible in Fluent reports >Report>Fluxes, or >Report>Surface integrals, I get a something totally different. I have no idea why..
Just for completness - simulation is unsteady, I just pick up some converged time step for confrontation..

Any idea? thank you very much in advance..

dmoroian · May 31, 2011, 04:06

Probably a typo: y =+ x
If you're using the above atribution with the intent of y = y+x; then is wrong. What it really means is: y = +x; or simpler y = x.

argeus · May 31, 2011, 14:08

no no, im sorry, just a typo.. i want to write y+=x..

May 27, 2011, 13:12	Fluent value vs UDF value discrepancy	#1
argeus New Member Ján Join Date: Mar 2010 Location: Slovakia Posts: 24 Rep Power: 16	hello hello, Any help highly appreciated.. please.. Im using a F_FLUX(t,tf) to extract data (mass flow rate) from fluent to a .txt file. x = F_FLUX (t,tf) access data from each elementary face. then I use a auxilliary variable, which sums the values from all elementary cells. looks like: y =+ x;. Now I have a total mass flow rate [kg/s] through a boundary face. But, when i try to compare this value with value accessible in Fluent reports >Report>Fluxes, or >Report>Surface integrals, I get a something totally different. I have no idea why.. Just for completness - simulation is unsteady, I just pick up some converged time step for confrontation.. Any idea? thank you very much in advance..

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May 31, 2011, 04:06		#2
dmoroian Senior Member Dragos Join Date: Mar 2009 Posts: 648 Rep Power: 20	Probably a typo: y =+ x If you're using the above atribution with the intent of y = y+x; then is wrong. What it really means is: y = +x; or simpler y = x.

May 31, 2011, 14:08		#3
argeus New Member Ján Join Date: Mar 2010 Location: Slovakia Posts: 24 Rep Power: 16	no no, im sorry, just a typo.. i want to write y+=x..