238 - Fire Fundamentals pt. 19 - Defining fires in your models

Welcome to another fire fundamentals episode! Today we dig into how to place a fire in a model so results reflect real physics. From plume inputs to FDS burners, we show where HRRPUA, radiative fraction, and D* make or break smoke your calculations. Things considered in this episode:

• why defining the design HRR is separate from placing the source
• what a flame is and why we cannot resolve its chemistry
• plume models compared by inputs: perimeter, Q, Qc
• entrainment, virtual origin, and effective diameter
• realistic HRRPUA ranges for building-scale fires
• radiative vs convective fractions and why they matter
• zone model linkage to plumes for smoke control
• volumetric smoke and heat sources for CFD: volume, placement, and limits
• fuel-based fires in CFD and oxygen constraints
• growth modeling via area expansion vs flux ramping
• soot yields, heat of combustion, and visibility
• D* and meshing guidance for credible resolution
• why predictive fire spread modelling for design use does not really exist...

Resources, resources!

• G. Vigne et al. "Review and Validation of the current Smoke Plume Entrainment Models for Large-Volume Buildings"
• W. Węgrzyński & M. Konecki "Influence of the fire location and the size of a compartment on the heat and smoke flow out of the compartment" - (this is a paper from my PhD where I explain the concept of volumetric heat source)
• M. Bonner et al. "Visual Fire Power: An Algorithm for Measuring Heat Release Rate of Visible Flames in Camera Footage, with Applications in Facade Fire Experiments"
• Episode 100 - Smoke plumes! That was a fun one.
• G. Heskestad "Fire Plumes, Flame Height, and Air Entrainment" from SFPE Handbook (also the source of the overlayed image on the cover showing range at which fires exist)

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