I'm doing some simulation using StarCD 3.24. A vent is extracting air from a room with heat source. The temperature of air will change with time. I want to control the vent flow rate using the temperature at a monitor cell in the air domain (that cell is far from the vent), e.g. if T > 500K, the vent flow rate is doubled. How to set up such a model? Thank for any input.

I would suggest the following:

1) Use the subroutine posdat.f (level 2) to monitor the temperature at a given cell location of your computational domain. You store the temperature value in a variable passed to other STAR-CD user subroutines via a COMMON block.

2) Use the subroutine BCDEFI.F if you defined the air vent as a inlet boundary condition (with negative entering velocity for modeling extraction) or FLUINJ.F if you extract fluid from within the computational domain. The flow rate can be then changed via some heuristic formula based on the measured temperature.

Hope this helps...