The development and mitigation of backdraft: a real-scale shipboard study

Gottuk, Daniel T.; Peatross, Michelle J.; Farley, John P.; Williams, Frederick W.

doi:10.1016/s0379-7112(99)00033-8

Cited by 57 publications

(28 citation statements)

References 5 publications

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“…As the flame penetrates the openings, it ignites the mixture outside the compartment, resulting in a fire ball or a blast wave. This explosion phenomenon in the building fire is termed backdraft [1]. The backdraft shows great threat for the safety of people, especially firefighters [2].…”

Section: Introductionmentioning

confidence: 99%

Simulation of gravity currents using the thermal lattice Boltzmann method

Yang

Junqi

Wang

2011

Numerical Methods in Fluids

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SUMMARYThe lattice Boltzmann method (LBM) is becoming an effective numerical technique of computational fluid dynamics (CFD). In this study, with some new thermal LBM schemes being proposed, the LBM is used to simulate the gravity current prior to backdraft (a particular and hazardous phenomenon in compartment fire) within laminar restrictions. The dimensionless time for gravity current traveling from the opening to the rear wall of a bench-scale compartment is calculated under different opening geometries, respectively, including: full end opening, upside-slot end opening, middle-slot end opening, downside-slot end opening, and slot ceiling opening. The application is very successful and the results show that the dimensionless time under the slot ceiling opening is the longest. Among the slot end openings, similar dimensionless time has been obtained for the upside-slot and middle-slot end openings, which is shorter than the downside-slot end opening. For the full end opening, the shortest dimensionless time is obtained. Finally, some valuable advices are given for fire protection engineering.

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Section: Introductionmentioning

confidence: 99%

Simulation of gravity currents using the thermal lattice Boltzmann method

Yang

Junqi

Wang

2011

Numerical Methods in Fluids

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“…If an opening occurs, for example a window breaks or firefighters open a door to the room, fresh oxygen is carried into it by gravity currents, and mixes with these gases. The mixing of gas with oxygen can create a flammable mixture resulting in ignition and an explosive or rapid combustion called backdraft [6][7][8][9][10]. The deflagration propagates, causing an extreme pressure build-up [11].…”

Section: Introductionmentioning

confidence: 99%

A CFD and Experimental Investigation of the Mixing Process in Compartment Fires

Guigay¹,

Most²,

ElÃ-asson³

et al. 2011

Fire Safety Science - Proceedings of the 10th International Sym

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The mixing of reactants, hot fuel-rich gas and cold air, by a gravity wave, is a complex hydrodynamic process essential in the initiation of hazardous conditions in an under-ventilated compartment fire. The mixing process is first studied by carrying out experiments on a specific enclosure, characterizing the gravity wave by means of particle image velocimetry measurements and fast tomography visualizations. The results are then used to calibrate and validate numerical and CFD models of these experiments. Both numerical and experimental methods permit to determine complex hydrodynamic processes such as Kelvin-Helmholtz instabilities and Van Karman vortices, and to quantify the mixing level in a fire compartment.

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“…This knowledge and the understanding of the warning signs identified just before backdraft occurs will lead to a more successful result in handling such situations. Until recently little research has been done on backdraft [1][2][3][4][5], except the work done by Fleischmann [2,3], in spite of how hazardous and dangerous this phenomenon is to fire-fighters. When an under-ventilated fire dies from a lack of oxygen, the enclosed room can remain full of hot unburnt gases.…”

Section: Introductionmentioning

confidence: 99%

The Use of CFD Calculations to Evaluate Fire-Fighting Tactics in a Possible Backdraft Situation

Guigay

Gojkovic²,

Bengtsson

et al. 2008

Fire Technol

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This paper is an attempt to integrate theoretical Computational Fluid Dynamics (CFD) calculations with practical fire-fighting tactics commonly used when arriving at the scene of an underventilated fire. The paper shows that CFD has a great potential in improving understanding and creating better effectiveness in the estimation of fire-fighting tactics. If burning has occurred in a lack of oxygen for a long time, excessive pyrolysis products may have accumulated in the fire compartment. If air is suddenly introduced in the compartment a backdraft may occur. The CFD code used for the simulations is fire dynamics simulator (FDS). In this paper, we focus on the conditions that can lead to backdraft, and not the deflagration or rapid combustion in itself. Therefore, the simulations focus on the gravity current and the mixing process between cold fresh air and hot smoke gases by considering a uniform temperature inside the building as initial condition. The different tactics studied include natural ventilation, positive pressure ventilation (PPV) and dilution by water mist. Their effectiveness is observed comparing them with a reference scenario, where no action is taken. The main objective of natural ventilation is to find the fire source, and the venting is more effective with several openings. Tactics involving PPV are very effective in evacuating the unburnt gases, but increases the mixing, and consequently the probability of backdraft during the early stage of operation. On the other hand, the addition of water mist can reduce the danger of backdraft by reducing the concentration of unreacted combustible gases below the critical fuel volume fraction (CFVF), where ignition cannot occur. If the dilution level is insufficient the danger of backdraft is increased, mainly because the process of gases evacuation is longer due to cooling, which reduces the density difference between hot and cold gases. During a fire-fighting operation, the choice of tactic depends mainly on whether there are people left in the building or not, but also on the fire-fightersÕ knowledge of the buildingÕs geometry and the fire conditions. If the situation shows signs of strongly underventilated conditions, the danger of backdraft has to be considered and the most appropriate mitigation tactics must be applied. 12 Nomenclature C airThe heat capacity of air (approximately 1 kJ/(kg K)) CFVF Critical fuel volume fraction CMC Critical mixture composition D(X) Dilution level, corresponds to a scenario with X % mass concentration GML Gas measurements line LFL Lower flammability limit M o Initial mass of hot gases M vap Mass of vapor added to obtain the desired dilution M CH4 Mass of unburnt gases (methane) Q fan Flow rate of the PPV fan tSimulation time T Temperature T final Temperature of hot gases after dilution T in Temperature of hot gases inside the compartment T out Temperature of cold gases outside the compartment (ambient) UFL Upper flammability limit v fan Velocity at the inflow boundary, due to PPV fan V gas Volume of hot gases in the en...

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The development and mitigation of backdraft: a real-scale shipboard study

Cited by 57 publications

References 5 publications

Simulation of gravity currents using the thermal lattice Boltzmann method

Simulation of gravity currents using the thermal lattice Boltzmann method

A CFD and Experimental Investigation of the Mixing Process in Compartment Fires

The Use of CFD Calculations to Evaluate Fire-Fighting Tactics in a Possible Backdraft Situation

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