volume flowrate integral

sajad_abasi · August 12, 2011, 03:49

hi to all.

i want to clculate following term in cfx that is time dependent quantity.
is it possible to calculate this term with out writing fortran code and if yes how??????????

""integral of ((Q-Qref)dt)"" where Q is flowrate at each time and Qref if refrence flowrate.........

pls help me in detail...

best regards

monkey1 · August 12, 2011, 04:10

Why not writing it as an Expression and then creating a Variable which takes as Value the result of the expression?

If you then activate the transient statistics in the CFX Pre Output menu, then it will write out the transient averages for each defined variable.
Or you set the Variable as the one to be monitored during the run and then you can export the plotted data of the solver into a .csv file.

Is this goin in the direction of your problem???

ghorrocks · August 12, 2011, 07:28

The easiest way to do this is to make a monitor point set to Q and write it out every time step. Then do the simulation and export the Q versus time graph and integrate it using excel, matlab or whatever you want.

sajad_abasi · August 12, 2011, 08:18

hi.
my problem exctely is a porous domain.in normal case flowrate is Qref.then suddenly the pressure at inlet decreased and so the flow rate is decreased.i need to calculate that integral or in an other word "sumation" to use it and set te porous resistance and obtain the referenced flowrate.

so in any time step i need sumation of flowrate in the all passed time.this is exactly what i want to do.

is there a way that i can do this?

thanks for your replies.

sajad_abasi · August 12, 2011, 08:27

the methods that you write is valuable when i want the summation as an outpout.

but i need it during the run to setup and change porous resistance.

i will be thankfull if you gide me

best regards

singer1812 · August 12, 2011, 10:02

It looks like you couldnt get the summation to work out within CEL. It should be straight forward and I dont see any reason why you are getting the error that you are getting.

Since you are have trouble with the CEL method, do the summation user fortran.

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August 12, 2011, 04:10		#2
monkey1 Senior Member Join Date: Jul 2011 Location: Berlin, Germany Posts: 173 Rep Power: 14	Why not writing it as an Expression and then creating a Variable which takes as Value the result of the expression? If you then activate the transient statistics in the CFX Pre Output menu, then it will write out the transient averages for each defined variable. Or you set the Variable as the one to be monitored during the run and then you can export the plotted data of the solver into a .csv file. Is this goin in the direction of your problem???

August 12, 2011, 07:28		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	The easiest way to do this is to make a monitor point set to Q and write it out every time step. Then do the simulation and export the Q versus time graph and integrate it using excel, matlab or whatever you want.

August 12, 2011, 08:27		#5
sajad_abasi Member sajad Join Date: Nov 2010 Posts: 51 Rep Power: 15	the methods that you write is valuable when i want the summation as an outpout. but i need it during the run to setup and change porous resistance. i will be thankfull if you gide me best regards

August 12, 2011, 10:02		#6
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	It looks like you couldnt get the summation to work out within CEL. It should be straight forward and I dont see any reason why you are getting the error that you are getting. Since you are have trouble with the CEL method, do the summation user fortran.