This blog compares the FED CO results generated using FDS devices with results generated using a Pathfinder agent.
FDS Model
A simple FDS model contains a fire source and two openings. Devices are placed at 1.75 m above the floor level near the vertical opening to measure the CO concentration in the air.
Pyrosim Model Details
Geometry
- Length = 10 m
- Width = 10 m
- Height = 3 m
- Cell size = 0.5 m x 0.5 m x 0.25 m
- Door opening = 1 m x 1.75 m (vertical opening at mesh boundary)
- Ceiling opening = 1 m x 1 m (horizontal opening at ceiling level for make up air)
Reaction
- Polyurethane – C6.3 H7.1 O2.1 N1.0
- CO yield = 0.05
- Soot yield = 0.1
Fire Surface
- HRRPUA = 2000 kW/m²
CO Measuring Devices
- Quantity – volume fraction
- Location – XYZ = 0.50, 0.75, Z=1.75
Simulation time
- Simulation time = 300
Output
- Plot3D – Carbon Monoxide
Pathfinder Model
Agent characteristics
- Height = 1.95 m (The measurement location for FED quantity sampling is 90% of occupant height; 1.95 x 0.9 = 1.755 m; FDS device height = 1.75 m)
Pathfinder Models
Pathfinder Model 1 – The final exit is positioned at approximately 0.25 m away from the edge of the Pyrosim model.
Pyrosim Model 2 – The final exit is at the edge of the Pyrosim model.
Coupling of FDS results with Pathfinder
Pathfinder can use the PLOT3D data output from FDS to couple FDS and Pathfinder. For this exercise, I enabled the PLOT3D option in FDS to measure CO concentration in the air.
Step 1: Import FDS file
Import FDS file to generate rooms
Step 2: Import Smokeview file
Import Smokeview file to couple Pathfinder model with FDS Plot3D results
Pathfinder Simulation
The Pathfinder model opened the final exit door at time = 300 seconds using a delay feature to measure agent exposure to CO concentration. 300 seconds is the total duration of the FDS simulation. The door is opened at 300 seconds to allow the agent to exit the door.
The approximate location of the agent in Pathfinder models was:
- Pathfinder model 1: x = 0.46 m, y = 0.74 m
- Pathfinder model 2: x = 0.22 m, y = 0.74 m
Comparision of FDS Device and Pathfinder Agent Data
Pathfinder Model 1 and FDS Device 1
- Pathfinder agent location: x = 0.46 m, y = 0.74 m, z = 1.755 m
- FDS device location: x = 0.5 m, y = 0.75 m, z = 1.75 m
Pathfinder Model 2 and FDS Device 2
- Pathfinder agent location: x = 0.22 m, y = 0.74 m, z = 1.755 m
- FDS device location: x = 0.25 m, y = 0.75 m, z = 1.75 m
Conclusion
The results extracted from FDS and Pathfinder are almost identical. The differences in the results may be attributed to the variation in the agent location compared to the FDS device location.
Files
FDS and Pathfinder files are available on my Github page: https://github.com/jabirjamal/jabirjamal.com/tree/main/FE/FED_CO_Pathfinder
References
https://support.thunderheadeng.com/docs/pathfinder/2021-3/user-manual/#_importing_fds_output_data
https://support.thunderheadeng.com/docs/pathfinder/2021-3/technical-reference-manual/
