"do loop" in cfx expression

sajad_abasi · August 2, 2011, 04:30

hi dear friends.

is it possible to write do loop by CEL in cfx?

the project is a tube with a porous domain at the end of that.
then the inlet pressure decreased suddenly and so the flowrate decreased. i want to change the resistance of the porous domain to obtain the initial flowrate and i need to have sumation of flowrate in all passed time.

i dont know if it is possible or not???????????

singer1812 · August 2, 2011, 10:44

Do-Loop isnt what you need. Follow this thread. It shows a method to do what you want within CEL. If you dont like this, you can use user fortran.

http://www.cfd-online.com/Forums/cfx...pressions.html

sajad_abasi · August 3, 2011, 10:20

hi singer 1812 and thanks for your help.

but im still confused.i do what you wrote me but i dont know how should i use the "res file" as an initial condition?

can you guide me?
another question for me is that after i add an additional variable and run one itration then should i add an expression??????

thanks again.

singer1812 · August 3, 2011, 14:29

You need to run an intial run, a "dummy" run if you will, needs only be one iteration, to initialize the variable that you want to addup. If you try adding up that variable, (ie. a=a+1), CFX will complain because a doesnt exist upon start.

If you make a dummy run, only needs to be 1 iteration, with a=0. Then use that run as an initialization for your real run (with a=a+1 or whatever you are using), then CFX will not complain.

sajad_abasi · August 3, 2011, 15:32

hi singer 1812
should i write "a=a+1" as a ""CEL expression"" or another "additional variable"?

i want to have sum of flowrate in all of the passed times.

i realy need that so if it is possible for you guide me in detail.

best regards

sajad_abasi · August 3, 2011, 19:39

hello

i see you posted a topic about "Update Loop = TRANS_LOOP" .

i want to sum the flow rate at all the time step passed but i dont know how...

i defined a AV by name of debi and add "Update Loop = TRANS_LOOP" to it in the "edit in command" part then i run for one iteration to have a given initial value for debi=0 then i defined a expression by name of "totdebi=debi+flowrate@inlet"

when i run it gives me error im really confused.
if it is possible for you give me help in detail

thanks.

August 2, 2011, 04:30	"do loop" in cfx expression	#1
sajad_abasi Member sajad Join Date: Nov 2010 Posts: 51 Rep Power: 15	hi dear friends. is it possible to write do loop by CEL in cfx? the project is a tube with a porous domain at the end of that. then the inlet pressure decreased suddenly and so the flowrate decreased. i want to change the resistance of the porous domain to obtain the initial flowrate and i need to have sumation of flowrate in all passed time. i dont know if it is possible or not???????????

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August 2, 2011, 10:44		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	Do-Loop isnt what you need. Follow this thread. It shows a method to do what you want within CEL. If you dont like this, you can use user fortran. http://www.cfd-online.com/Forums/cfx...pressions.html

August 3, 2011, 10:20		#3
sajad_abasi Member sajad Join Date: Nov 2010 Posts: 51 Rep Power: 15	hi singer 1812 and thanks for your help. but im still confused.i do what you wrote me but i dont know how should i use the "res file" as an initial condition? can you guide me? another question for me is that after i add an additional variable and run one itration then should i add an expression?????? thanks again.

August 3, 2011, 14:29		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	You need to run an intial run, a "dummy" run if you will, needs only be one iteration, to initialize the variable that you want to addup. If you try adding up that variable, (ie. a=a+1), CFX will complain because a doesnt exist upon start. If you make a dummy run, only needs to be 1 iteration, with a=0. Then use that run as an initialization for your real run (with a=a+1 or whatever you are using), then CFX will not complain.

August 3, 2011, 15:32		#5
sajad_abasi Member sajad Join Date: Nov 2010 Posts: 51 Rep Power: 15	hi singer 1812 should i write "a=a+1" as a ""CEL expression"" or another "additional variable"? i want to have sum of flowrate in all of the passed times. i realy need that so if it is possible for you guide me in detail. best regards

August 3, 2011, 19:39		#6
sajad_abasi Member sajad Join Date: Nov 2010 Posts: 51 Rep Power: 15	hello i see you posted a topic about "Update Loop = TRANS_LOOP" . i want to sum the flow rate at all the time step passed but i dont know how... i defined a AV by name of debi and add "Update Loop = TRANS_LOOP" to it in the "edit in command" part then i run for one iteration to have a given initial value for debi=0 then i defined a expression by name of "totdebi=debi+flowrate@inlet" when i run it gives me error im really confused. if it is possible for you give me help in detail thanks.