Fire dynamics includes the study of the basic chemical, physical, and thermodynamic phenomena involved in fire development, behaviour, propagation and suppression. Concepts from chemistry and physics, coupled with the fundamentals of heat and mass transfer, are used to understand how structures and components will react under fire conditions, as well as to characterize ignition, fire growth and spread, and fire severity in various environments. Research also involves the study of the interactions between a fire and its environment, including aspects of fire ventilation, suppression, heat transfer from fires and transition from fire to explosion.
Large Scale Fire Testing
The full scale fire research program applies basic scientific principles of fire science to develop new understanding of the behaviour of structural and transportation fires, to study fire initiation and spread, methods for fire detection and suppression, and many related issues. Results influence the fire service and fire engineering communities through improved understanding of the impact that new suppression agents and methods, wind, ventilation, construction materials, building layout and structural design have on fire growth and spread.
Large-scale fire research takes place at the University of Waterloo Live Fire Research Facility, in the large test enclosure which has the necessary space (3975 ft2 floor area and ~ 4 storeys high) and equipment to accommodate and instrument very large-scale fire experiments with or without the effects of wind. Located at one end of the test area are 6 fans (6.3 m x 7.8 m outlet area) which can generate winds up to 13 m/s across the experiment. The large test building has been used for studies of aviation fuel spill fires occurring close to a plane fuselage; however, we are very interested in extending this work into other areas related to transportation safety as well as into new research initiatives related to building and structural fires in support of performance based codes.
Medium-scale pool fire research
The medium-scale pool fire research program has involved both experimental and numerical investigations into liquid fire behaviour. On the experimental side, flow visualization, two component LDA and thermocouples have been used to simultaneously measure temperatures and velocities in two orthogonal directions at over 125 stations in 0.3 m diameter (medium-scale) acetone (radiative) and methanol (non-radiating) pool fires. Turbulence quantities and estimates of mean vorticity have been derived from the data.
Future research includes investigations of fire radiation and soot (particulate) formation, potentially using new diagnostics for soot characterization, as well as radiation and species concentration measurements. Interpretation of the results has led to increased understanding of the detailed physical structure and mechanisms of air entrainment at the base of the fire.
To complement the experimental program, LES and RANS based computational models of the pool fire are being developed. These codes are configured to solve the unsteady, three-dimensional conservation equations over a non-orthogonal solution domain. Provision will be included for choice of fuel, different boundary conditions, the form of the turbulence model and variations in the combustion and radiation sub-models. Results will be verified against available experimental data.
Complementary research in the behaviour of large-scale liquid fuel spill fires typical of those encountered in transportation accidents or industrial spills is underway. This combined experimental and numerical approach to the study of fire behaviour at multiple scales should, over the longer term, facilitate development of fire scaling laws and prediction of fire behaviour under a variety of ambient and boundary conditions.
Fire Suppression
Practical aspects of fire suppression and fire-hoseline interactions are studied through joint research and training exercises with municipal and naval fire fighter personnel. Tests have been performed in abandoned houses to study residential sprinkler effectiveness. The effects of different suppression agents and hose strategies (i.e. wide vs. narrow angle, direct vs. reflected application) on the thermal environment during suppression of enclosure fires has been studied in the University of Waterloo Live Fire Research Facility, as well as in field fire experiments. Through full-scale research in realistic operating conditions, training modules are delivered directly back to fire service personnel demonstrating key elements of suppression methodologies and facilitating better explanations of the complex interactions between their suppression activities and the thermal environment in a burning structure.
One of the most rewarding aspects of the fire suppression studies to date was to hear back from a young fire fighter that, while in the midst of fighting a devastating town house fire, he recalled our research debriefing on wide vs. narrow angle fog suppression and acted to minimize the chance of steam build-up while still effectively suppressing the fire!
The Fire Research Group plans to continue research on different suppression agents and methodologies, fire sprinkler and detection systems, and positive pressure ventilation strategies for fire control.
Gas Explosions
Natural gas is used throughout North America as an energy source for heating and industrial process applications. When leaks occur from the supply system or from appliances within an enclosed space, explosive mixtures can result, creating a significant hazard to occupants and capital investment, as well as to gas company and emergency response personnel who might be called to investigate the reason for the leak. In research aimed toward development of safer operational procedures for dealing with a build up of natural gas in a residence, a series of experiments were conducted in which isolated houses were filled with natural gas, vented and ultimately exploded to study the effects of the explosion on the structures and their contents.
This multi-agency research effort included:
- Investigation of migration of natural gas in dwellings,
- Evaluation of the effectiveness of ventilation in mitigating a build up of natural gas in a dwelling,
- Evaluation of the survivability of arson, fraud, forensic and homicide evidence in the event of an explosion, and
- Study of the dynamics of natural gas explosions in dwellings.