Issues with airflow not showing in simulation, basic room airflow modeling

[sbeckersmrt]

I am new to the software. Working on a clean room space with ceiling air supply and chemical hoods exhausting the air. The ceiling supply grilles  I have setup with air as a material set as variable and an assigned flow rate and temp. The exhaust portions of the model are setup as air set as variable with a 0 psig pressure. The interior of the room is a closed space with that air volume set as variable as well. When I run the model there is no air flowing from the supply grilles and the 0 psig return grilles have velocity vectors that face into the space.

Any ideas? I am sure its just something simple that I have setup wrong.

Thanks

Stephan

[Jon.Wilde]

Hi Stephan,

To confirm:

All air volumes are connected to one another and set to air?

All air volumes are meshed?

All Boundary Conditions (BC's) are applied to the external boudnaries of the domain, where air enters/exits the model yes? (We cannot have internal surface BC's)

How many iterations are you running for?

If you are running forced convection and natural convection will have minimal effect there would be no need to run with air_variable - this only comes into play when you have internal heat gains/losses and a low flow rate (less than 1m/s or so and you would also need gravity on).

Kind regards,

Jon

[sbeckersmrt]

Thanks for the reply, I am think my issue is some of my boundary conditions are not external. I am fixing that now and about to run it again.  I have been using 100 interations, dose that seem reasonable for a room airflow model?

Thanks again

[Jon.Wilde]

Sounds good. We typically recommend more, maybe 300-500 and before that point, CFD should have stopped automatically at a converged solution.

[sbeckersmrt]

I think I have the model setup per your instruction above. Before I when I had internal boundry conditons the model wotuld run but produce wacky results. After fixing the model I now get an error message when the model is run saying there is an issue with the mesh. It recommends checking the geometry or fixing the mesh. I am sure my issue is just something I have setup wrong in the model.

I opened a support case yesterday, #08209476 and recieved a link to the FTP site. I just uploaded the model to that site.

Thanks for the help--Stephan