Unbalanced airflows

[cargo3]

Hi,

I am getting 'Unbalanced flows' when I want to run the simulation on my model. There seems to be missing some flow out as the message indicates a difference of -9.85 mi/s.

What is this due from?

Thanks!

[huntervu28]

Air check should be zero, it means total air in and out = 0.

[liamh]

I am getting 'Unbalanced flows' when I want to run the simulation on my model. There seems to be missing some flow out as the message indicates a difference of -9.85 mi/s.

For mass conservation flow into the CFD model has to equal flow exiting so if you get a flow imbalance it could be because of:

1) you have added supplies and extracts that have a net flow into the room to positively pressurise a room. That extra flow has to get out somewhere so for ease increase the extracts to match the supplies.
2) if you have natural ventilation predicted by Macroflo when you import the boundary conditions some of these flows have not been set up in the Microflo model. There is a "Minimum opening size" and "Minimum opening flow" number in the boundary import window. Try reducing these values to see if any small inflows are then included. If this doesn't work then you can compatre the supply and extract boundary conditions set up by Microflo for windows to the flows as given by VISTA to see if some of the window boundaries have failed to come in. It is vary rare for this to happen though but sometime very long a thin windows fail to come in.
3) you have imported the boundary conditions and then joined your zones together. It is very important to do the following in the correct order:
a) highlight the CFD zones in "Output options" in the apacheSim window
b) run apacheSim
c) export the timestep needed from VISTA
d) in mIcroflo join the zones together into a CFD domain
e) import the boundary conditions

If you do any of this out of order it is possible to get a flow imbalance.