Kevin B. Mcgrattan

• National Institute of Standards and Technology

This paper discusses important input parameters used by the Fire Dynamics Simulator, a computational fluid dynamics (CFD) model of fire. Suggestions are made for new or enhanced submodels and measurements specifically for CFD models of fire.

A method for the large-eddy simulation (LES) of wildfire spread over complex terrain is presented. In this scheme, a cut-cell immersed boundary method (CC-IBM) is used to render the complex terrain, defined by a tessellation, on a rectilinear Cartesian grid. Discretization of scalar transport equations for chemical species is done via a finite volu...

A series of compartment fire experiments is described in which a square natural gas burner was positioned in a corner or against a wall and gradually moved towards the room center to assess the relative effects on the plume and compartment temperatures. The experiments were conducted to validate computational fluid dynamics simulations that were pe...

We developed a neural-network based zonal method (RADNNET-ZM) for analysis of thermal radiative heat transfer in combustion environments. • Accounts for both the non-gray effect of emitting/absorbing species and the geometric effect of any 3-D Cartesian enclosures • Accurate and numerically efficient • Easy to be implemented Studies show RADNNET-...

The fire industry relies on fire engineers and scientists to develop materials and technologies used to either resist, detect, or suppress fire. While combustion processes are the drivers for what might be considered to be fire phenomena, it is heat transfer physics that mediate how fire spreads. Much of the knowledge of fire phenomena has been enc...

The National Institute of Standards and Technology (NIST) conducted an extensive investigation of the collapse of the three tall World Trade Center (WTC) buildings. A central part of this investigation was the reconstruction and understanding of the initiation and spread of the fires. This paper describes the reconstruction of the fires, the therma...

An overview of a methodology for simulating fires and other thermally-driven, low-speed flows is presented. The model employs a number of simplifications of the governing equations that allow for relatively fast simulations of practical fire scenarios. The hydrodynamic model consists of the low Mach number large-eddy simulation subgrid closure with...

The overall uncertainty of a model prediction is a combination of the uncertainty of the input parameters and the uncertainty of the model assumptions. The former is referred to as parameter uncertainty; the latter model uncertainty. A method for quantifying model uncertainty is proposed for complicated numerical models that are not amenable to mor...

A reaction time scale model is developed for use in the eddy dissipation concept (fast chemistry limit) closure of the mean chemical source term in large-eddy simulation of fires. The novel aspect of the model is to consider a scaling regime for coarse mesh resolution based on buoyant acceleration. The model computes local time scales for diffusion...

The Fire Dynamics Simulator (FDS) and Smokeview (SMV) are compu-tational and visualization tools specifically designed for large-eddy simulations (LES) of low-speed, thermally driven flows. 1 FDS Version 6 will offer improvements in the turbu-lence model (dynamic Smagorinsky 2, 3), the wall model (Werner Wengle 4), and the scalar transport scheme (...

CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE) is a U.S. Nuclear Regulatory Commission Office of Research program to quantify the mass and energy released from burning electrical cables. This type of quantitative information will be used to develop more realistic models of cable fires for use in fire probab...

The NIST Fire Dynamics Simulator is a variable-density large-eddy simulation code tuned for low-speed fire dynamics and heat transfer. The gas-phase numerics utilize a Cartesian staggered-grid arrangement and are generally second- order accurate. Until now, complex geometry has been treated with an immersed boundary method in which objects in the f...

A common technique in computational fluid dynamics (CFD) modeling of fire is to assume single step, infinitely fast combustion, in which case the transport equations of all gas species can be combined into one for a single conserved scalar called the mixture fraction. While this approach is adequate for many engineering applications, for fire scena...

Recent testing by the Building and Fire Research Laboratory of the National Institute of Standards and Technology collected a large dataset of species, temperature, velocities, and heat fluxes for a wide range of fuels burning at varying degrees of ventilation inside a reduced scale enclosure. This dataset is extremely well documented with uncertai...

This document was developed in the frame of the 'International Collaborative Project to Evaluate Fire Models for Nuclear Power Plant Applications' (ICFMP). The objective of this collaborative project is to share the knowledge and resources of various organizations to evaluate and improve the state of the art of fire models for use in nuclear power...

One of the recommendations of the National Construction Safety Team (NCST) for the Federal Building and Fire Safety Investigation of the World Trade Center Disaster [NIST NCSTAR 1 Final report on the collapse of the World Trade Center Towers. NCST for the Federal Building and Fire Safety Investigation of the World Trade Center Disaster, National In...

This paper summarizes a recently completed project sponsored by the U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research (RES) including collaborative efforts conducted by both Sandia National Laboratories (SNL) and the National Institute of Standards and Technology (NIST). The project is known as the Cable Response to Live Fire...

The paper presents numerical simulations of a fire in the Howard Street Tunnel, Baltimore, Maryland, following the derailment of a freight train in July, 2001. The model was validated for this application using temperature data collected during a series of fire experiments conducted in a decommissioned highway tunnel in West Virginia. The peak pred...

A numerical method is developed for the transport of polychromatic radiation in polydisperse sprays. The method is implemented within a wide-band radiation solver using the Finite Volume Method. Mie theory is used to compute the absorption and scattering characteristics of the water droplets. The solver is designed to be computationally effective b...

Fire dynamics simulations of a 7.1-cm buoyant turbulent diffusion flame were performed using a mixture-fraction-based combustion model. In our previous work, good agreement between the measured and the calculated fire flow field was achieved with carefully selected domain and grid sizes using a Lagrangian thermal-element combustion model. The Lagra...

A large-scale fire experiment was conducted to assess the accuracy of a combination of gas and solid-phase models designed to predict the temperatures of structural steel elements exposed to a fire. The experiment involved a 2 MW heptane spray fire in a compartment that was nominally 4 m by 7 m by 4 m tall. The compartment openings were designed su...

Black PMMA was burned in the cone calorimeter in two orientations (horizontal and vertical), at imposed radiant heat fluxes of (0, 5, 10, 25, 50, and 75) kW/m2, and the visual appearance, flame size, heat release rate, and mass loss rate were recorded. Various other experimental parameters were varied. The topography of the burned samples was also...

Current trends in computational fluid dynamics (CFD) modeling of fire are discussed, in particular the widening communication gap between model developers, model users, and the larger fire protection engineering community in regard to combustion and turbulence. The paper suggests steps that can be taken by all of these groups to improve the current...

Acceleration disturbances or g-jitter exist in all reduced gravity experimental platforms. These disturbances often have a fully three-dimensional orientation and are transient. An important element in experimental design, therefore, is a determination of how sensitive the physical processes under investigation may be to the expected g-jitter. Very...

Black PMMA was burned in the cone calorimeter in two orientations (horizontal and vertical), at imposed radiant heat fluxes of (0, 5, 10, 25, 50, and 75) kW/m 2 , and the visual appearance, flame size, heat release rate, and mass loss rate were recorded. Various other experimental parameters were varied. The topography of the burned samples was als...

A combination of numerical modeling and large-scale experimentation has yielded a tremendous amount of information about the structure, trajectory and composition of smoke plumes from large crude oil fires. A numerical model, a large outdoor fire plume trajectory (ALOFT), has been developed at NIST to predict the downwind concentration of smoke and...

Computer modeling and visualization are important tools for understanding the processes of fire behavior. Fire models range in complexity from simple correlations for predicting quantities such as flame heights or flow velocities to moderately complex zone fire models for predicting time-dependent smoke layer temperatures and heights. Zone fire mod...

A computational fluid dynamics (CFD) model of fire and smoke transport is described. Combustion is represented by means of a single conserved scalar known as the mixture fraction. Radiation transport is approximated in the gray gas limit. The algorithms have been incorporated in the Fire Dynamics Simulator (FDS), a computer program maintained by th...

In this project a transient, fully three-dimensional computer simulation code was developed to simulate the effects of realistic g-jitter on a number of combustion systems. The simulation code is capable of simulating flame spread on a solid and nonpremixed or premixed gaseous combustion in nonturbulent flow with simple combustion models. Simple co...

Improvements have been made to the combustion and radiation routines of a large eddy simulation fire model maintained by the National Institute of Standards and Technology. The combustion is based on a single transport equation for the mixture fraction with state relations that reflect the basic stoichiometry of the reaction. The radiation transpor...

Based on preliminary assumptions and analysis, mathematical models have been used to estimate the behavior of the fires in the twin towers of the World Trade Center (WTC) on September 11, 2001. The hijacked-plane collision with each tower produced significant structural damage, generated a spectacular external fireball, and started burning within t...

In cooperation with the fire protection engineering community, a computational fire model, Fire Dynamics Simulator (FDS), is being developed at NIST to study fire behavior and to evaluate the performance of fire protection systems in buildings. The software was released into the public domain in 2000, and since then has been used for a wide variety...

The objective of this work was to provide measurements from reduced-scale experiments for use in the NIST Fire Dynamics Simulator, a computational fluid dynamics model that calculates fire growth, spread, sprinkler activation, and water suppression of rack-storage commodity fires. The model requires implementable sub-grid algorithms and correspondi...

The thermal environment in small and moderate-scale pool flames is studied by Large Eddy Simulation and the Finite Volume Method for radiative transport. The spectral dependence of the local absorption coefficient is represented using a simple wide band model. The predicted radiative heat fluxes from methane/natural gas flames as well as methanol p...

Three-dimensional large eddy simulations (LES) of two buoyant flows were performed in conjunction with a Smagorisky turbulence model. The flows included a non-reacting helium plume previously simulated with two-dimensional simulations and a methane/air turbulent diffusion flame. In comparison with the previous two-dimensional simulation results, th...

Enclosure effects on the transition from a localized ignition to subsequent flame growth over a thermally thin solid fuel in microgravity are numerically investigated by solving the low Mach number time-dependent Navier-Stokes equations. The numerical model solves the two and three dimensional, time-dependent, convective/diffusive mass, and heat tr...

An efficient large eddy simulation algorithm is used to compute surface pressure distributions on an eleven story (target) building on the NIST campus. Local meteorology, neighboring buildings, topography and large vegetation (trees) all play an important part in determining the flows and therefore the pressures experienced by the target. The wind...

A three-dimensional large-eddy-simulation computational fluid dynamics (CFD) program, developed for studying the transport of smoke during a fire in an enclosure, is applied to four flow problems relevant to nonfire situations. This evaluation is relevant to the use of the program for indoor air quality modeling as well as its use in modeling the e...

ABSTRACT This paper addresses community-scale fires, which have also been called urban/wildland interface or inter- mix fires. These fires arise when,wildland fires invade the built environment,and attack structures as well as wildland fuels. The prediction of the spread of wildland fires, such as those occurring out West during the summer of 2000,...

Enclosure effects on the transition from a localized ignition to subsequent flame growth over a thermally thin solid fuel in microgravity are numerically investigated by solving the low Mach number time-dependent Navier-Stokes equations. The numerical model solves the two and three dimensional, time-dependent, convective/diffusive mass, and heat tr...

A numerical fire model, Fire Dynamics Simulator (FDS), is being developed at NIST to study fire behavior and to evaluate the performance of fire protection systems in buildings. To date, about half of the applications of the model have been for design of smoke handling systems and sprinkler/detector activation studies. The other half consists of re...

Localized ignition is initiated by an external radiant source at the middle of a thermally thin sample under external slow flow, simulating fire initiation in a spacecraft with a slow ventilation flow. Two ignition configurations are simulated, one across the sample surface creating a line shaped flame front (two-dimensional, 2-D, configuration) an...

The agent concentration required to achieve the suppression of low strain rate nonpremixed flames is an important consideration for fire protection in a microgravity environment such as a space platform. Currently, there is a lack of understanding of the structure and extinction of low strain rate (<20 s(exp -1)) nonpremixed flames. The exception t...

A number of facilities are available for microgravity combustion experiments: aircraft, drop towers, sounding rockets, the space shuttle, and, in the future, the International Space Station (ISS). Acceleration disturbances or g-jitter about the background level of reduced gravity exist in all these microgravity facilities. While g-jitter is routine...

In this study, a laboratory-scale facility has been developed to screen the suppression effectiveness of agents that are delivered in a transient fashion such as solid propellant gas generators. The transient application, recirculating pool fire (TARPF) agent effectiveness screen features a propane fire stabilized behind an obstruction, which is kn...

For more than a decade NIST conducted research to understand, measure and predict the important features of burning oil on water. Results of that research have been included in nationally recognized guidelines for approval of intentional burning. NIST measurements and predictions have played a major role in establishing in situ burning as a primary...

A numerical investigation of swirling fire plumes is pursued to understand how swirl alters the plume dynamics and combustion. One example is the 'fire whirl' which is known to arise naturally during forest fires. This buoyancy-driven fire plume entrains ambient fluid as heated gases rise. Vorticity associated with a mechanism such as wind shear ca...

A methodology for simulating the dynamics of large industrial fires in the outdoor environment is presented. The large eddy simulation techniques developed by the authors and their collaborators are used to simulate a fire on top of a large oil storage tank adjacent to several neighboring tanks. The governing equations are modified to account for t...

suppression effectiveness under conditions that relate to field applications. In this study, a laboratory-scale facility has been developed to screen the suppression effectiveness of agents that are delivered in a transient fashion, such as solid propellant gas generators. The facility features a pool fire stabilized behind an obstruction, which is...

Naturally occurring fire whirls are rare but highly destructive phenomena. These are mostly generated by the interaction between a buoyant fire plume and its surroundings. The whirling motion generated can enhance the plume length and sustain burning. In this paper, we report the results of a numerical investigation of whirling fues generated in ve...

The International Fire Sprinkler, Smoke & Heat Vent, Draft Curtain Fire Test Project orga- nized by the National Fire Protection Research Foundation (NFPRF) brought together a group of industrial sponsors to support and plan a series of large scale tests to study the interaction of sprinklers, roof vents and draft curtains of the type found in larg...

The effects of multiple fire plumes in a stably stratified atmosphere with a uniform wind are investigated. A parabolized approximation of the steady state Navier-Stokes equations obtained by replacing the windward velocity component with the ambient wind speed is the basis of the model. Lagrangian particles are used to visualize the flow, account...

This paper describes a procedure for model-based analysis and coding of both left and right channels of a stereoscopic image sequence. The proposed scheme starts with a hierarchical dynamic programming technique for matching across the epipolar line for efficient disparity/depth estimation. Foreground/background segmentation is initially based on d...

In order to clarify the mixing that occurs in a gravity current which precedes a backdraft, a two-dimensional simulation, a series of salt water experiments, and backdraft experiments were performed. A compartment in a ratio width/height/length of 1/1/2 is used in the experiments and computations. Two different openings were used in the salt water...

The effect that the wind's vertical variation has on fire plume behaviour is investigated. A parabolized set of governing equations are discretized using finite differences to arrive at the numerical model. Lagrangian particles are used to visualize the flow, account for atmospheric fluctuations and determine the smoke concentration field. A parame...

The purpose of this investigation is to examine the feasibility of using computed tomography to evaluate the predictive capabilities of fire models. In this pursuit, we have analyzed data from both laboratory- and computer-generated plumes in order to determine the number of line-of-sight measurements, the detector topology, and the temporal resolu...

An approach to field modeling of fire phenomena in enclosures is presented. The conservation equations of mass, momentum and energy are calculated with sufficient temporal and spatial resolution to yield a truly three-dimensional, dynamic picture of the fire plume and its surroundings. The large-scale eddies are simulated directly and sub-grid scal...

Ignition of solid fuels by external thermal radiation and subsequent transition to flame spread are processes that not only are of considerable scientific interest but which also have fire safety applications. A material which undergoes a momentary ignition might be tolerable but a material which permits a transition to subsequent flame spread woul...

Several regions in the United States have begun the process of obtaining preapproval to use in-situ burning as a remediation method for oil spills. The Building and Fire Research Laboratory of the National Institute of Standards and Technology (NIST) under the sponsorship of the Minerals Management Service has conducted a research program to study...

The velocity and temperature fields of fire plumes are studied theoretically and computationally using the authors' large eddy simulation techniques. A version of the Navier-Stokes equations specialized to the study of fire dynamics is used as the basis for the analysis. No empirical turbulence modeling parameters are introduced into the computatio...

The purpose of this study is to examine the predictive capabilities of fire models using the results of a series of fire experiments conducted in an aircraft hangar with a ceiling height of about 15 m. This study is designed to investigate model applicability at a ceiling height where only a limited amount of experimental data is available. This an...

A three dimensional model was developed to describe the scalar structure which exists in a countercurrent turbulent diffusion flame. The model was solved numerically by combining CHEMKIN thermochemical and transport databases within the CFX4.3 software. The distance between the axis of the upper oxidiser duct and the lower fuel duct, termed eccentr...

The numerical solution of the Navier-Stokes equations specialized to the study of fire dynamics is used to assess the interaction of sprinklers, vents and draft curtains in a large enclosure, such as a warehouse. Simplifications of the three-dimensional, time-dependent equations permit high resolution solutions that can be compared with experimenta...

The open thermosyphon has several characteristics which makes it suitable for verification of CFD codes. Prior experimental research has provided data suitable for bench-marking case histories, furthermore, in spite of its simple natural circulation flow geometry, the open thermosyphon exhibits complicated flow behavior. In this study two different...

Combustion in buoyancy-driven fire plumes is assumed to be diffusion controlled and described by a mixture fraction variable. Experimental data for a 10-cm methanol pool fire was compared to numerical results obtained by assuming the plume was axially symmetric. No turbulence model was used. The influence of imposing axial symmetry independent of t...

An experimental and numrical investigation of ignition and the subsequent transition to flame spread over a thermally thin cellulosic sample is described. The experiments were conducted using a lamp as an external radiant source in a 50% oxygen atmosphere at three diffeirent wind velocities of 0.2, and 5 cm/s in a 10 s drop tower. The results show...

A large eddy simulation (LES) model of smoke plumes generated by large outdoor pool fires is presented. The plume is described in terms of steady-state convective transport by a uniform ambient wind of heated gases and particulate matter introduced into a stably stratified atmosphere by a continuously burning fire. The Navier-Stokes equations in th...

A two-dimensional, time-dependent model is developed describing ignition and the subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. The effects of a slow external wind (0–5 cm/s), and of the flux distribution of the external radiation on the transition are studied...

An approach to the study of gas phase combustion and convec- tion processes in fires using a combination of mathematical analysis and computer simulation is presented. It seeks to solve the gov- erning equations dkectly (if approximately) by decomposing the fire into a large scale convective and radiative transport problem coupled to a small scale...

The engine nacelle in an aircraft encases the jet engine compressor, combustors, and turbine. A nacelle fire is typically a turbulent diffusion flame stabilized behind an obstruction in a moderately high speed air flow. The fuel source for a fire in the nacelle are leaking pipes carrying jet fuel or hydraulic fluid that can feed the fire either as...

A large eddy simulation model of smoke plumes generated by large outdoor pool fires is presented. Theplume is described in terms of steady-state convective transport by a uniform ambient wind of heated gases and particulate matter introduced into a stably stratified atmosphere by a continuously burning fire. The Navier-Stokes equations in the Bouss...

An axisymmetric, time-dependent model is developed describing auto-ignition and subsequent transition to flame spread over a thermally-thin cellulosic sheet heated by external radiation in a quiescent microgravity environment. Due to the unique combination of a microgravity environment and low Reynolds number associated with the slow, thermally ind...

This viewpoint paper considers the potential of offshore burning of oil in the recent Tampa Bay spill as a generic oil spill response option. While the oil spilled might not have been amenable to burning, the physical constraints of the spill and subsequent environmental conditions provide a scenario for future consideration of this option.

An approach to the study of gas phase combustion and convection processes in fires using a combination of mathematical analysis and computer simulation is presented. It seeks to solve the governing equations directly (if approximately) by decomposing the fire into a large-scale convective and radiative transport problem coupled to a small-scale the...

A two-dimensional Boussinesq model describing heat-driven, buoyant convection in a polygonal enclosure is presented. The hydrodynamic model is based on the time-dependent Navier-Stokes equations with constant viscosity and thermal conductivity; no turbulence model or other empirical parameters are introduced. The polygonal domain is mapped via a nu...

The fundamental processes involved in ignition and flame spread have been extensively studied, they are generally studied separately without combining ignition and flame spread through the transition process. Moreover, the majority of the flame spread studies assume steady state flame spread. To study the transient aspects of ignition and the trans...

A method of studying the large scale transport of smoke and hot gases induced by fires in enclosures is described. The approach is based on solving the governing equations directly (if approximately) by decomposing the fire-driven flow field into large scale convective and small scale combustion components. In this work, results involving large sca...

During the past q0 years, there has been much discussion of the relative merits of the potential and the Euler formulations of the equations of motion of transonic flow over supercritical wing sections. To study the two models in a common framework, a finite difference version of the Euler solver has been incorporated into the potential code . The...

We explore the consequences of moist convection on Jupiter with a one-dimensional version of the cumulus parameterization used in the GISS general circulation model. The model predicts the collective effects of an ensemble of moist convective plumes on a conditionally unstable atmosphere. Heating/cooling and drying/moistening of the large-scale env...

A three-year research effort has been conducted as part of the Next Generation Program (NGP) to develop a laboratory screening device suitable for predicting the behavior of halon alternatives in full-scale fire suppres- sion experiments. Most of the work has focused on the transient delivery of gaseous agents and interactions with an obstacle-stab...

In cooperation with the fire protection engineering community, a numerical fire model, Fire Dy- namics Simulator (FDS), is being developed at NIST to study fire behavior and to evaluate the performance of fire protection systems in buildings. Version 1 of FDS was publicly released in February 2000, and Version 2 in December 2001 (1, 2). To date, ab...

A numerical fire model, Fire Dynamics Simulator (FDS), is being developed at NIST to study fire behavior and to evaluate the performance of fire protection systems in buildings. To date, about half of the applications of the model have been for de- sign of smoke handling systems and sprinkler/detector activation studies. The other half consists of...

In the present report, experimental data collected at two sets of mesoscale burns are compared with the results of the LES model run using the recorded meteorological and physical conditions. The two experiments are the Newfoundland Offshore Burn Experiment (NOBE), Aug. 1993, and the Alaska Clean Seas Burning of Emulsions, Sept. 1994. Each series o...