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-   -   How to simulate valve with pressure BC? (http://www.cfd-online.com/Forums/fluent/41447-how-simulate-valve-pressure-bc.html)

Luk June 20, 2006 01:27

How to simulate valve with pressure BC?
 
Hi all, I have following problem. The geometry is very simple: air enters the pipe from one side under pressure. On the other side there is valve: the valve could be in one of two positions: "closed" where no flow is possible (pipe closed from one side) and "opened" where sucking occurs through the valve. The valve opens and closes periodicaly. I am using UDF to represent changes of the valve state in time but I dont know how to simulated closed valve with pressure BC.

Any ideas? Luk

Gernot June 20, 2006 02:31

Re: How to simulate valve with pressure BC?
 
Why donīt you change your pressure outlet to wall and backwards ?

Luk June 20, 2006 03:46

Re: How to simulate valve with pressure BC?
 
Is it possible with UDF? I mean is it possible to periodicaly change type of BC for specified surface/face?

Gernot June 20, 2006 04:47

Re: How to simulate valve with pressure BC?
 
I didnīt work much with UDFīs. But Iīm sure you can handle that with a journal file. The question is how often do you open and close?

Luk June 20, 2006 06:12

Re: How to simulate valve with pressure BC?
 
About 100/sec. The size of the pipe is few cm in diameter and about 50cm length. Pressures are rather low.


Gernot June 20, 2006 06:46

Re: How to simulate valve with pressure BC?
 
O.K., i tried some things. To change the boundary condition with a journal file is possible. To start the journal file with an execute-comand works too. So there is a posibility to automate the whole thing but itīs a long way.

Maybe someone else knows an alternative.


Luk June 20, 2006 07:07

Re: How to simulate valve with pressure BC?
 
Dear Sir, Thanks for Your kind help! I'll try this solution today in few hours.

Luk

Gernot June 20, 2006 07:25

Re: How to simulate valve with pressure BC?
 
last chance for me to help you is tomorrow, then Iīm on holiday for 2 weeks - Jippie!!!!

The execute comand to start the journal is easy :

file read-journal nameofjournal

the journal comands to switch from wall to pressure outlet :

define boundary-condition modify-zones zone-type ( ID number of your face you want to switch ) pressure-outlet ( or wall when you switch back )

but be careful the settings of your pressure outlet are set to the default values. you can change them with :

define boundary-condition pressure-outlet

good luck

Luk June 20, 2006 08:06

Re: How to simulate valve with pressure BC?
 
I wish Your nice holydays! Could You be so kind and send me email for further contact: my address is Lukasz.Czopyk@ifj.edu.pl. I promise not to disturb Your free time anyway.:)

Luk


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