UDF Help!

littlelz · July 2, 2013, 08:29

I am new on UDF. Just wonder if anybody can help me.

I have an velocity inlet boundary, and an outlet pressure boundary. I need to setup the outlet pressure is a fixed ratio to inlet pressure. As inlet pressure is calculated in running, and the outlet pressure will be varied with it. I am thinking to use UDF to achieve it. But how, I ahev no idea. Could anybody give me some clue. I know how to setup a varied inlet velocity by UDF. thanks

blackmask · July 2, 2013, 20:36

So you are solving the compressible flow problem?
Technically

Code:

DEFINE_EXECUTE_AT_END

along with

Code:

DEFINE_PROFILE

and a file scope variable could do the job, but you need be more concerned on the physical interpretation of the boundary condition as such.

littlelz · July 3, 2013, 04:42

many thanks, blackmask.

I am doing a compressible flow simulation. It is a single fan blade, the pressure ratio is 1.455. That's why I am considering a outlet pressure condition, which will be related to inlet pressure by 1.455. The inlet is velocity inlet boundary. am I right?

July 2, 2013, 08:29	UDF Help!	#1
littlelz New Member Join Date: Mar 2009 Posts: 24 Rep Power: 17	I am new on UDF. Just wonder if anybody can help me. I have an velocity inlet boundary, and an outlet pressure boundary. I need to setup the outlet pressure is a fixed ratio to inlet pressure. As inlet pressure is calculated in running, and the outlet pressure will be varied with it. I am thinking to use UDF to achieve it. But how, I ahev no idea. Could anybody give me some clue. I know how to setup a varied inlet velocity by UDF. thanks

July 2, 2013, 20:36		#2
blackmask Senior Member Join Date: Aug 2011 Posts: 421 Blog Entries: 1 Rep Power: 21	So you are solving the compressible flow problem? Technically Code: DEFINE_EXECUTE_AT_END along with Code: DEFINE_PROFILE and a file scope variable could do the job, but you need be more concerned on the physical interpretation of the boundary condition as such.

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July 3, 2013, 04:42		#3
littlelz New Member Join Date: Mar 2009 Posts: 24 Rep Power: 17	many thanks, blackmask. I am doing a compressible flow simulation. It is a single fan blade, the pressure ratio is 1.455. That's why I am considering a outlet pressure condition, which will be related to inlet pressure by 1.455. The inlet is velocity inlet boundary. am I right?