Fire modelling and risk analysis

Fire modeling and risk assessment are important tools to predict, and design measures to minimize, both direct and indirect losses due to fire. Risk assessment, either qualitative or quantitative, is a major task in any framework developed for fire safety management. Fire risk must be assessed quantitatively to determine fire safety measures that provide acceptable levels of protection to life and property. Quantitative risk assessment is also necessary for performing cost-benefit analyses on proposed safety measures and for determining optimal fire safety designs.

Many different mathematical models can be employed in predicting fire behaviour and in quantitative assessment of fire risk. The models can be deterministic or non-deterministic. Deterministic models include engineering correlations, zone, field and CFD models, which are based on scientific theories and experimental results. Non-deterministic models, generally based on data from real fire incidents, are statistical, probabilistic, stochastic simulations or models related to the likelihood of fire spread and damage and probabilistic models concerned with the reliability of fire protection measures. In all cases, uncertainties caused by key factors involved in predicting the development of the fire, behaviour of building occupants during a fire and/or operation of fire protection systems should be included in the model to provide a quantitative evaluation of fire risk and effectiveness of fire safety measures.

Consolidated Fire and Smoke Transport Model (CFAST) and Fire Dynamics Simulator (FDS) fire models

Consolidated Fire and Smoke Transport Model (CFAST)

The CFAST model is a zone model that predicts, based on a specified fire source, the evolution of temperatures, certain species concentrations and the hot upper-cooler lower layer interface heights in a multi-compartment structure. CFAST was developed by the Building and Fire Research Laboratory of NIST.

Researchers in the University of Waterloo Fire Research Group use CFAST to simulate the development of the thermal environment and interface heights in experimental fire scenarios they have conducted in the field and at the Live Fire Research Facility. CFAST modeling is regularly applied in the design of live fire scenarios and structural fire experiments, for the main test enclosure in the LFRF, and for characterization of numerous fire fighter training towers (i.e. the WRESTRC Fire Training FacilityOakville Fire Training Facility, and Department of National Defence Naval Fire Training Structures).

Fire Dynamics Simulator (FDS)

FDS is a Computational Fluid Dynamics (CFD) model of fire-driven fluid flows. It uses a Large Eddy Simulation (LES) formulation of the Navier-Stokes equations appropriate for simulations of low-speed, thermally-driven flow and tailored specifically to smoke and heat transport from fires. Smokeview is a visualization program used in conjunction with FDS to graphically represent the simulation results. FDS and Smokeview were developed by the Building and Fire Research Laboratory of NIST.

Researchers in the UWaterloo Fire Research Group use FDS to simulate the development of the thermal environment, as well as aspects of smoke movement and heat transfer in various full-scale field fire scenarios. It is also applied to predict specific fire cases (Pool fires and Aviation fuel fires) that can be applied to experimental data. This allows identification of potential improvements in the sub-models and implementation of any modifications needed to better simulate the full range of complex real fire scenarios.

The UWaterloo Fire Research Group is always interested in extending their modelling efforts into new areas, including computer-based assessment of alternative structural design options, as well as fire service and fire protection engineering applications.

Computational modeling for fires

The computational modeling of fires involves the development and implementation of new mathematical models and sub-models to solve problems related to the simulation of turbulent mixing, flame stabilization and pollutant emissions in fires. Currently, the Large Eddy Simulation and RANS models incorporated into several commercial CFD codes are being applied by the Fire Research Group in modeling experimental pool fire and transportation spill fire scenarios. Prediction of specific fire cases and comparison of the results to detailed experimental data obtained in our on campus laboratory and large-scale fire research areas has led fire research to identify improvements in the sub-models and to implement the modifications needed to better simulate complex real-life fire scenarios.

fire model in simulation

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