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Nevill Krik July 28, 2004 00:53

Air movements in the room
Dear Experts,

I'm a bit new as a CFX user, so don't be too severe to my question.

I try to make a simulation of a air inside the room. There are ventilation inlet and outlet. At the outlet I suggest the constant air speed at the outlet and the pressure=0 at the inlet.

There is central heating radiator below the window. I set the temperature of the radiator, window and the ambient air.

I need the air velocity picture inside the room. I have problems with the convergence of the solution - I cant drop the RMS for the moments below 10e-3 - 10e-4. And what is more - during the solution the CFX built the wall in the inlet and totally close it:

------------ A wall has been placed at portion(s) of an INLET boundary condition (at 97 % of the faces, 96 % of the area) to prevent fluid from flowing out of the domain. The boundary condition name is: DoorGap. The fluid name is: Air Ideal Gas. ---------

I tried both steady state and transient simulation. The situation persists. It looks like the turbulence has the main role in the behaviour.

I don't understand what's wrong with my model. It is just like the simulation in CFX 5.7 tutorial...

Do you have and suggestions?

Thank you!

test July 28, 2004 03:36

Re: Air movements in the room
It would be easier to help you if you can post your .out or your ccl file in the forum. You can as well take the help from your local CFX support person.

Nevill Krik July 28, 2004 09:02

Re: Air movements in the room
The last out file from the transient solutin has 307kb size. I don't think it's normal to post it here. What ccl file do you mean?

Glenn Horrocks July 28, 2004 18:16

Re: Air movements in the room
Hi Nevill,

The warning message you are getting is because flow is going out an inlet. It generally causes convergence problems so you should try to fix it.

Two options: Move your inlet further upstream to where there is no backflow. The inlet will then only see forward flow and will behave itself much better. The alternate option is to use an opening. Openings allow backflow, but can be a little harder to converge and is not as accurate as the first option (if you can do it).


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