Fire simulation plays a critical role in understanding building fire dynamics, informing safety design decisions, and validating fire protection strategies. This project presents a computational fire simulation of a residential structure subjected to a Ultra-Fast fire scenario. The simulation models a fire with a heat release rate of 1000 kW/m² and a ramp-up time of 73 seconds (as per Ultra fast fire alpha value) from ignition to peak intensity.

This simulation analyzes fire dynamics, NFPA mitigation strategies, and structural impact under these extreme conditions, providing valuable data for fire safety engineering and emergency response planning.

We will evaluate key NFPA standards including fire resistance ratings, egress time requirements, structural integrity thresholds, and smoke management criteria. The simulation results will be systematically compared against established NFPA benchmarks to determine whether the modeled structure meets prescribed safety standards for life safety, property protection, and structural performance.

This compliance-focused methodology will provide a framework for assessing fire safety design effectiveness and identifying potential areas requiring improved fire protection measures to meet NFPA (e.g., NFPA 101, NFPA 72, NFPA 13, NFPA 92) requirements.

The FDS software is  

FDS uses a cartesian mesh. The mesh size is a critical criteria in FDS, infact in all general purpose CFD simulations. In cases of fire it becomes specifically important as capturing heat plumes and smoke spread is particularly important in case of fire as it involves safety of people. 

Since FDS uses an LES based simulation there are mainly two things to be taken care of while performing Simulations.

1) Characteristic Fire Diameter (D*) : It is a non-physical length scale related to the heat release rate (HRR) of a fire. It characterizes the size of the fire’s buoyant plume relative to the ambient environment and is the primary metric used to determine the required computational grid resolution (mesh size) for a Large Eddy Simulation (LES).  The formula for characteristic fire diameter is given as,

To determine the cell size (dx) , FDS recommends that the (D*/dx) should be between 4 and 16.

2) Resolution of eddies: Since FDS is base on the LES, the mesh size has to be set so that 80% of the eddies are resolved.

Tenability Criterias

1) Visual Tenability: Visual tenability is defined as the capacity of occupants to visually locate escape routes under emergency conditions. Smoke obscuration shall therefore be limited such that doors and walls are discernible at a minimum distance of 10 m(generally measured at a height of 2m).

2) Air Velocity Tenebility: During emergency mode operation in any underground transit space, the air velocity along evacuation routes shall not exceed 11.0 m/s. 

3) Fractional Effective Dose (FED): This exposure to carbon monoxide can be expressed as a fractional effective dose. For a weak person, FED =0.3 shows incapacitance.

Simulation Results