HVAC Simulation Grinding to a Halt

[GeorgeBGrant]

Hi All! I've used PyroSim to generate a fire compartment model (~ 2,500 m3) with explicit leakages (i.e. holes in the walls) totalling ~ 1 m2. The fire grows to around 11 MW and thereafter becomes ventilation controlled in agreement with previous CFAST simulations. I have since added an HVAC extract network to the model and defined the fire compartment as Zone01 but left the air leaks as described. The HVAC network is connected to several other volumes (ranging from 20 ~ 70 m3) which are defined as separate pressure zones & have leakage area ratios (Aleak/Awalls) of the order 10-6, which I appreciate is maybe pushing the model somewhat as I've seen Jason Floyd's comment previously that the HVAC model expects leakage ratios to be in the range 10-3 ~ 10-4, however I've run the model without a fire and the HVAC system seemed to run OK. Incidentally these smaller volumes also have steady air injection rates of around 5 l/s throughout the simulation. Now I've added the fire compartment to the simulation the run has stuck on timestep 250s of 850s. I'm wondering if it's my use of explicit leakage definition in the fire compartment, the very small leakage ratios elsewhere or maybe that the extraction vent in the fire compartment is struggling due to its proximity to the fluctuating flame zone on that boundary? Any help would be gratefully received!

[drjfloyd]

We would need the fds (not pyrosim) input file simplified as much as possible while still keeping the error.

[GeorgeBGrant]

Thanks Jason. I'll have a look & simplify as much as possible then post the .fds info.