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Romek March 6, 2011 20:42

inlet temp = outlet temp

I have an urgent problem with my cfx setup.

I am using Ansys 13 CFX Workbench. My problem is I want to set the inlet temperature as it is at the domains outlet, so it is like a circle. The fluid is being warmed up in that domain.

I have read I have to use a DEFINE_PROFILE UDF in that case. But I never used UDFs before and I do not have enough time to search for a good tutorial.

Please can someone help me how to set up my analysis to solve my problem.

Inlet name: Oil Inlet
Outlet name: Oil Outlet

Or do you have a link to a turorial or another method how to solve this?



Romek March 7, 2011 01:42

Just figured out I can do it via Expressions.

The Statement would be "Tin = areaAve(Oil.T)@Oil Outlet"

Can someone confirm this?

ghorrocks March 7, 2011 19:54

Looks OK. Have you considered using a periodic boundary condition?

Romek March 7, 2011 20:55

whats is the difference of the periodic boundary condition?

right now i have a static temperature at the inlet calculated by the expression above.

Romek March 7, 2011 22:01

i have an other problem.

i am simulating the oil flow in an engine. So the pressure level in the galleries ishould be over 3 bar depending on the engine revs. But the pressure level in the oil pan should be atm.
When I simulate it as one domain the pressure level in the galleries is ok, but in the oil pan region drops to -0.6 bar rel. pressure. Inlet/Outlet mass flow (which is the same) control the boundary conditions. The domain contains oil and air.
What is the best way to set up these conditions? Split it up in 2 domains?
Or create an opening for pressure control in the oil pan?

afrit March 9, 2011 03:23

plz help
Hi, I think i have a similar problem to define my boundary conditions

i have two narrow long pipes in contreflow configuration so in total i have 4 fluid boundaries to declare in CFX-pre (2 inlets and 2 outlets).

well I know the inlet conditions of the first pipe (Temp, pressure and Mass flow rate) Tin1, Pin1, mRin1

As for the second tube inlet conditions i'd like to define them as similar to the first pipe's outlet (Temp, Pressure and mass flow rate)
i.e: Tin2=Tout1, Pin2=Tout1, ...

How i Can do that I'm quite new user of CFX and i don't know how to define this inlet conditions in CFX-pre. probably with expression right ?
can you send me the right tutorial or defintion if possible

thank you

Romek March 9, 2011 21:10

@ afrit: download "Ansys CFX Reference Guide" for that. You will find it in Chapters 14/15.

Please can someone help me with my problem?

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