How to change the boundary condition at a certain time?

masoud90 · February 21, 2014, 01:18

Hi everyone,

I want to simulate the air motion with ANSYS FLUENT in a cylinder which has 2 valves. The inlet valve has to be closed at a certain time let's say t0 and the outlet has to be opened at this time.

How can I change the boundary condition of inlet from inlet to wall and the boundary condition of outlet from wall to outlet at the time t0?

Hope someone can help me out. Thanks.

Kina · February 21, 2014, 17:44

what you probably want is a UDF for your transient analysis. There is a tutorial for using UDFs for fluent that you might wanna consider. Also, http://aerojet.engr.ucdavis.edu/flue...df/node231.htm might be useful for you. pay attention to parallelizing the udf when running fluent parallel.

masoud90 · February 21, 2014, 18:33

Thank you Kina,
Actually my problem is the outlet ! I don't want to have a outlet until the time t0,I mean the fluid before time t0 only has inlet valve. after t0 I want to have outlet in different place from the inlet....do you have any suggestion ?
Thanks

Kina · February 22, 2014, 11:53

There has been a thread with code for such an action. As I don't understand much of scheme programming, I can only guess what most of the code does but maybe you should give it a try.
http://www.cfd-online.com/Forums/flu...tion-type.html
I'll have a look at it when I have more time next week but with the code in the other topic you should be able to figure most of it out.

masoud90 · February 23, 2014, 14:56

Thank you for the link. it is helpful.

February 21, 2014, 01:18	How to change the boundary condition at a certain time?	#1
masoud90 New Member masoud Join Date: Jan 2014 Posts: 4 Rep Power: 12	Hi everyone, I want to simulate the air motion with ANSYS FLUENT in a cylinder which has 2 valves. The inlet valve has to be closed at a certain time let's say t0 and the outlet has to be opened at this time. How can I change the boundary condition of inlet from inlet to wall and the boundary condition of outlet from wall to outlet at the time t0? Hope someone can help me out. Thanks.

February 21, 2014, 17:44		#2
Kina Senior Member Alex Join Date: Jan 2014 Posts: 126 Rep Power: 12	what you probably want is a UDF for your transient analysis. There is a tutorial for using UDFs for fluent that you might wanna consider. Also, http://aerojet.engr.ucdavis.edu/flue...df/node231.htm might be useful for you. pay attention to parallelizing the udf when running fluent parallel. masoud90 likes this.

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February 21, 2014, 18:33		#3
masoud90 New Member masoud Join Date: Jan 2014 Posts: 4 Rep Power: 12	Thank you Kina, Actually my problem is the outlet ! I don't want to have a outlet until the time t0,I mean the fluid before time t0 only has inlet valve. after t0 I want to have outlet in different place from the inlet....do you have any suggestion ? Thanks

February 22, 2014, 11:53		#4
Kina Senior Member Alex Join Date: Jan 2014 Posts: 126 Rep Power: 12	There has been a thread with code for such an action. As I don't understand much of scheme programming, I can only guess what most of the code does but maybe you should give it a try. http://www.cfd-online.com/Forums/flu...tion-type.html I'll have a look at it when I have more time next week but with the code in the other topic you should be able to figure most of it out.

February 23, 2014, 14:56		#5
masoud90 New Member masoud Join Date: Jan 2014 Posts: 4 Rep Power: 12	Thank you for the link. it is helpful.