Reference

NBSIR 85-3252

A Program for the Development

of A Benchmark Compartment

Fire Model Computer Code

Leonard Y. Cooper, John A. Rockett, Henri E. Mitler and David W. Stroup

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

October 1985

-QC

100

• U56

85-3252

1985

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 85-3252

MES eesearch kformatiom

CENTER

A PROGRAM FOR THE DEVELOPMENT

OF A BENCHMARK COMPARTMENT

FIRE MODEL COMPUTER CODE

Leonard Y. Cooper, John A. Rockett, Henri E. Mitler and David W. Stroup

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

October 1985

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
:
TABLE OF CONTENTS

Page

Abstract 1

1. INTRODUCTION 1

2. AVAILABLE COMPARTMENT FIRE MODELS 2

3. THE BENCHMARK COMPARTMENT FIRE MODEL DESIGN GUIDES 3

3.1 General Characteristics and Principal Intended Use of

the BCFM 3 3.2 Complexity of the Enclosure 5 3.3 Modeling Detail of the Physical Phenomena: The Code's

Module of Physics Subroutines

3.3.1 Compartment Fire Models and Compartment Fire

Model Computer Codes 7 3.3.2 Two Kinds of Modeling Detail 7 3.3.3 The Appropriate Level of Modeling Detail for

the BCFM 8

3.3.4 Coding Standards for the Module of Algorithm

Subroutines 12

3.4 The Numerics Software Module 12

3.5 The User Interface Module and User Manual Documentation ... 13

3.6 The Structure of the Computer Code 14

3.7 Guidelines for BCFM Flexibility 14

4. EXAMPLES OF THE ANTICIPATED USE OF THE BCFM 15

5. ACTIVITIES REQUIRED FOR MODEL DEVELOPMENT 18

6. SHORT-TERM AND LONG-TERM OBJECTIVES 20

6.1 A Two-Stage Effort in Software Development 20

6.2 The First Stage Effort - Testing Ideas on a Prototype

One-Room Compartment Fire Model 20

6.3 The Second Stage Effort - The BCFM 21

7. SUMMARY 21

8. REFERENCES 23

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'
A PROGRAM FOR THE DEVELOPMENT OF A BENCHMARK COMPARTMENT

FIRE MODEL COMPUTER CODE

Leonard Y. Cooper, John A. Rockett, Henri E. Mitier and David W. Stroup

Abstract

With a variety of objectives in mind, many different compartment fire

model computer codes have been developed within the fire saf ety/research

community. Yet, no one of these can be described as being a "benchmark" model

in the sense that it is reliable enough to be accepted as a standard of reference for the performance of design-oriented fire models. It is the major

objective of the Compartment Fire Modeling Research (CFMR) Group in the Fire

Safety Technology Division of the Center for Fire Research (CFR) to develop

such a Benchmark Compartment Fire Model (BCFM) computer code. This paper

describes the characteristics of this BCFM, and outlines the program which

will lead to its development.

1 . INTRODUCTION

The Compartment Fire Modeling Research (CFMR) Group in the Fire Safety

Technology Division of the Center for Fire Research (CFR) was established with

the major objective of developing a zone-type Benchmark Compartment Fire Model

(BCFM) computer code for simulating compartment fire-generated phenomena.

While many different types of compartment fire models are available for fire

safety design analyses as well as for fire research, it is the "benchmark"

quality of compartment fire simulations that is a focus of activities of the

CFMR Group. It is the purpose of this paper to describe the characteristics

of the BCFM computer code, and to outline the program of research which wi I I

lead to its successful development.

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2. AVAILABLE COMPARTMENT FIRE MODELS

There are a number of compartment fire models now in existence. The

Harvard and NBS/Harvard family [1-4], COMPBRN [5-7], FAST [8,9], RFIRES [10],

DACFIR [11], UNDSAFE [12], and many others. Each has its advantages and

disadvantages. Examples of these follow. A comprehensive review of available

models is beyond the scope of this paper, and the reader is referred to other

articles, e.g., references [13-16], where comparisons between models are

presented in substantial detail.

The Harvard-based models (the single room models, Mark 5 and 5.N, and the

multiroom models, Mark 6 and 6.N) are the most detailed in terms of the number

of dynamic effects taken into account, and they treat most of these phenomena

with reasonable accuracy. The models are time-dependent (rather than steady

or quasi-steady), and they use fairly robust numerical schemes. They are the

closest things now available to benchmark models.

COMPBRN is a quasi-steady model. It takes account of fewer physical

processes than do the Harvard-based models, and generally with less accuracy.

Thus its capability for accuracy is limited. It uses a prescribed fire with

some options including empirical parameters to represent energy feedback, fuel

porosity and spread rate. It is very fast.

FAST is a multiroom/ multilevel model. It deals only with prescribed

fires, it does not take the heating of target items into account, and it does

not consider forced ventilation. However, it treats the transport of gases

from room to room well, and has excellent associated graphics.

- 2 -
RFIK.ES is similar in concept and construction to the Harvard-based codes,

but over the last several years it has not been kept current with advances in

compartment fire modeling. The input data has to be carefully tailored to the

particular fire scenarios of interest. Although upper layer temperatures are

reasonably well predicted by RFIRES, its ability to simulate target object

temperatures accurately requires further development.

DACFIR was developed specifically for aircraft interiors. It calculates

the propagation of a fire over a seat in a different way than do the Harvardbased models, and it is potentially better in this regard. It is unique in

that it considers smoldering combustion.

UNDSAFE is the only field model to be mentioned here, although numerous

others exist. Field models in principle can more faithfully represent

physical reality than can zone models. In practice, however, the size and

speed of computers typically limit simulations to the order of 10^ nodes.

Thus, for a 3x4x2. 5m compartment, the primitive cells would be about

15 x 20 x 10 cm on a side, a rather crude representation of the space, for

many purposes. Moreover, the calculations for the same simulation time take

several orders of magnitude longer than those made with zone models.

3. THE BENCHMARK COMPARTMENT FIRE MODEL DESIGN GUIDES

3.1 General Characteristics and Principal Intended Use of the BCFM

The BCFM and its associated computer code are intended for use as a

standard of reference for other zone-type compartment fire models. A second

-3 -
intended use is to make very reliable predictions. It should be superior to

other contemporary models with regard to its ability to accurately simulate

the physics and chemistry of compartment fires. It should be numerically

robust, i.e., it should converge with high reliability to the solution of its

equation set for a broad spectrum of input data, and it should be readily

transferable to computer hardware facilities generally available to the fire

science and technology community. It need not necessarily execute with high

speed, since production calculations are not one of its intended uses. The

BCFM code should be well-documented and "user-friendly" in the sense that it

is readily usable by skilled practitioners familiar with compartment fire

simulations and related data sources. Finally, the computer code should have

an internal structure which is flexible in the sense that it facilitates

enrichment of the physics and chemistry included, and the numerics used. This

flexibility will allow the code to be usable as a vehicle for testing new

physical/chemical process algorithms. Also, such flexibility will permit

relatively frequent official and published updates of the BCFM, allowing it to

be readily maintained at a technical level which is current in relation to

advances in fire science.

The above paragraph describes important characteristics of the BCFM

computer code in a general and open-ended manner. In principle, no explicit

bounds of accuracy, completeness, etc. should be placed on any aspect of the

BCFM to be developed. Yet, to develop the model and its computer code, limitations in scope must inevitably come into play. For example, limitations in

scope are required to make BCFM development objectives compatible with CFMR

program resources. Toward these ends, some bounds will be required on the

physical complexity of the compartment spaces which the BCFM will handle, and

-4 -
on the number of and accuracy with which individual processes will be treated.

Other items whose scope requires clarification are the type of numerics used

for solving the governing BCFM equations, guidelines on the design of the user

interface, and those items which are relevant to the design or structure of

the computer code itself. All of these bounds and limitations will be

discussed below.

The BCFM development program will be carried out with the clear

recognition that developing a benchmark model and computer code must be viewed

as a continuing, long-term process. Nevertheless, the tasks described here

will be directed toward the development of a definite product, referred to

throughout this paper as the BCFM. Within the context of past and anticipated

future progress in fire science, it is recognized that a more appropriate

designation might be the next generation BCFM.

3.2 Complexity of the Enclosure

Consider a fire in a room (compartment) or grouping of rooms of a

building or other enclosure. The physical enclosure of interest here would

include those portions of the building which influence the characteristics of

the enclosure environment (i.e., environments with conditions significantly

different from the ambient) as it develops during the course of the fire.

Frequently the outside environment will influence the fire conditions, and in

such instances it must be involved in an analysis of compartment fires.

The enclosure of interest would include all compartments which

communicate with one another in such a manner as to affect the flow ol venti-

-5 -
lating air to and/or combustion products from the compartments actually

involved in the fire. In this sense most spaces of a building could be a part

of the enclosure. However, for many purposes this broad interpretation of the

extent of the enclosure is unnecessary. For example, while there is a strong

coupling between fire growth and the fire-generated environment in rooms of

fire involvement, and, possibly, in "freely connected" adjacent spaces, the

coupling in real fires between fire growth and conditions in "distant" spaces

is typically rather weak [17,18]. On the other hand, fire-generated phenomena

in rooms of fire involvement and in adjacent, connected spaces influence

strongly properties and rates of generation of hot and toxic products of

combustion which are key to the development of hazardous conditions in such

"distant" spaces.

The focus of the BCFM is on a capability for providing benchmark

simulations of fire growth phenomena and of the fire-generated environment in

rooms of fire involvement. In view of the above discussion, it is also

important that the BCFM be capable of simulating conditions which develop in

rooms "nearby" to the rooms of fire involvement. Finally, consistent with its

focus there is no strong requirement for the BCFM to treat "distant" spaces.

By excluding "distant" spaces, thereby limiting compartment complexity, a

significant simplification in BCFM scope is achieved. Relative to the

question of compartment complexity, all of the latter guidelines have been

adopted for the BCFM.

- 6 -
3.3 Modeling Detail of the Physical Phenomena:

The Code's Module of Physics Subroutines

3.3.1 Compartment Fire Models and Compartment Fire Model Computer Codes

Many different and often strongly coupled physical and chemical processes

occur during a compartment fire. A compartment fire model is a set of equations or algorithms which describe these individual processes. The couplings

between the different physical and/or chemical processes must be reflected by

similar coupling between their mathematical descriptions. Certain features of

compartment fire phenomena lend themselves to relatively simple mathematical

descriptions. Yet, except for the very simplest of compartment fire models,

computer-aided calculations are required to solve the model equations, i.e.,

to obtain a mathematical simulation of the compartment fire phenomena of

interest. Such calculations require a compartment fire model computer code

which is designed to solve the equations describing the physical/chemical

processes. The equations are represented by subroutine software which make up

a key module of the code.

3.3.2 Two Kinds of Modeling Detail

There are two kinds of detail which characterize the modeling capability

of any particular compartment fire model. These define the essence of an

overall fire model, and are useful in distinguishing one model from another.

The first kind of detail involves the number and types of processes taken

account of. The second kind of modeling detail is related to the ability of

algorithms to produce accurate simulations. Such reliability would be established, for example, through experimental validation.

- 7 -
It is possible to develop a model with a major focus on the detail

achieved through the inclusion of as large a number of processes as possible,

even though this will require that some of the algorithms, although physically

based, are not-well proven. To justify this approach, one can argue that the

resulting model would lead to simulations, which, although potentially

inaccurate, achieve an overall acceptability by accounting for the effect of

many interacting processes in a rational way. Alternatively, it is possible

to develop a model involving detail obtained from exclusive use of highly

accurate algorithms (which would presumably model the dominant processes in

fire scenarios of special interest). Such a model would ignore many obvious,

but presumably secondary, processes. To justify the latter kind of model one

can reasonably argue that a strong sense of accuracy, albeit for only limited

conditions, is fundamental if the results of compartment fire model simulations are to be taken seriously.

It is evident that a balance must be struck when addressing the question

of which kind of modeling detail to stress in the BCFM. As will be discussed

below, the BCFM will be designed with some flexibility in this regard.

Nevertheless, in terms of a general guideline, accuracy in algorithm simulation is the focus most consistent with the idea of a benchmark model. It is

this focus which will be adopted for the BCFM, and which will be a major

feature distinguishing the BCFM from other available compartment fire models.

3.3.3 The Appropriate Level of Modeling Detail for the BCFM

The notion of mathematically describing processes with "appropriate

detail" is now introduced. The task at hand is to identify guidelines which

-8-
would lead to a level of detail which is both appropriate for the BCFM, and

consistent with available resources. This must be done with an eye on code

flexibility, and with the focus on modeling accuracy in mind.

Fire science and technology dealing with compartment fire processes is

relatively young. It is reasonable to anticipate many decades of significant

advances in the ability to understand and simulate these processes. At the

present time compartment fire processes can be placed into three different

classes:

1. Processes already understood to the extent that at least minimally

accurate algorithms exist and have been tested.

2. Processes like those in class 1, but for which no suitable algorithms

exist; and processes which, while not well understood, have been

identified as being important, and which are already under serious

investigation in the fire research community.

3. Processes which have been identified as being important, but for which

no adequate investigations have yet been made (e.g., the principal

variables on which the process depends have not yet been identified).

Note that current and future research will eventually change the category

of any given process now in classes 2 or 3. Also, while the class 1 processes

are already reasonably well understood, it is likely that even for these,

future theoretical and experimental studies will lead to a capability for even

higher accuracy in their current simulation [19].

- 9-
To include class 3 processes in a new model would generally require that

it include certain "open-ended" features. Such features, set in place for the

purpose of contingency planning, might lead to excessive developmental

resource requirements. For this reason, only processes in classes 1 and 2

will, by design, be included in the BCFM. Thus, no special allowances will be

made in the BCFM to anticipate the direction of future research on compartment

fire processes. Note that this limitation in scope does not preclude the

possibility of eventually including some current class 3 processes in the BCFM

as they become better understood.

Class 1 processes will be included in the BCFM. Algorithms successfully

used in the Harvard-based computer codes [1-4] will be taken as a guide for

the accepted extent of this class, although algorithms from other sources will

be included as well. The catalog of Harvard-based algorithms will also be

used as a guide for the acceptable degree of modeling accuracy. In view of

the BCFM focus on "benchmark quality", however, some of these algorithms will

require significant improvements, and, possibly, the introduction of

additional variables. Some examples of NBS/Harvard algorithms requiring

improvements include those which describe:

® plume dynamics

® burning in the upper layer

o forced ventilation

• convective heat transfer to ceilings

® mixing between upper and lower layers due to the inward and outward

components of vent flows

® combustion product generation rates

- 10-
The flexibility of the structure of the computer code will be developed

so that, to the extent practicable, improvements to these algorithms will be

easy to incorporate into the BCFM. However, the improvements which can thus

be made will be limited. Eventually the need will arise for a new generation

of BCFM, which will be able to transcend these limitations, and incorporate a

wider class of improvements.

The following is a partial list of class 2 compartment fire-related

processes which will eventually be included in the BCFM:

o fire growth and spread on vertical surfaces

o radiation absorption of near-surface pyrolysis products

® mixing between layers and convective heat transfer to walls due to

wall flows

® heat transfer to floors and floor heating

o sprinkler link response

o detector response

The above two lists are only partial, and other processes may be

included. Over the course of BCFM development, additional processes that are

not now obvious are also likely to be added to the second list. However, the

addition of entries to either of the lists cannot be open-ended, since each

such addition must be matched with corresponding extensions in the BCFM

development time interval. The situation will, of necessity, lead to known

gaps in BCFM capabilities. For example, while better algorithms for the

processes of fire growth and flame spread on horizontal surfaces are future

necessities, such algorithms do not appear to be at hand. It is for this

- 11 -
reason that they are not identified above for improvement and inclusion into

the BCFM.

3.3.4 Coding Standards for the Module of Algorithm Subroutines

All physical processes included in the BCFM will be represented as

entries in a catalog of subroutine software. In the development of the

Harvard 6 multi-room fire model [2], considerable effort was expended in

establishing and implementing coding standards for these subroutines. These

standards are consistent with state-of-the-art computer software practices,

and should be directly applicable to the BCFM computer code.

3.4 The Numerics Software Module

The solutions for the coupled equation sets of the physical/cheraical

compartment fire processes will be carried out by the numerics software of the

BCFM computer code. When making such software choices for the new code, the

experience with the numerics software of the Harvard-based codes [1-4,22] will

be taken into consideration.

The numerics of the NBS/Harvard 6 codes are derived from an algebraicand differential-equation solver developed by C.W. Gear [3,20]. Certain

aspects of these numerics might still be considered state-of-the-art.

However, it is likely that improvements are now achievable. For example, as

suggested by D. O'Leary [21], while the variable elimination procedure developed for the Harvard 6 numerics [2,22] may reduce the number of unknowns, the

implicit assumption that the smaller variable set can be more readily solved

- 12 -
may not always be true; indeed, it may have the disadvantage of making the

resulting system of equations more difficult to solve. However, there are

techniques which can modify Gear's routines to take advantage of the sparse

Jacobian matrix generated in the calculation. The Juggle routine used in

Harvard 6 [2,22] is one such technique. Others might lead to an improved

approach for solving the BCFM system of equations. The objective would be to

make the code more reliable than it would otherwise be, possibly faster, and

easier to understand and modify.

In general, it is necessary that a review of the state-of-the-art of

relevant numerics software be carried out as a preliminary step in the

development and adoption of an optimal design for the BCFM numerics module.

3.5 The User Interface Module and User Manual Documentation

A well-designed user interface module and supporting user manual

documentation will be key to the user-friendliness of the BCFM computer code.

If these are developed to a high quality, much will have been done to insure

the code's broadest possible utility within the community of its intended

use. In recent years there have been significant advances in user interface

software practices, not taken fully advantage of in available compartment fire

model computer codes. Some of these new procedures would be directly relevant

to the BCFM computer code.

A variety of material property, fire growth, and other data will be

required as input to the BCFM [23]. A user-interface module capable of

accessing an independently maintained base of such data would be a particular-

- 13 -
ly attractive feature of the BCFM. Having this would minimize and often

eliminate the need for the user to refer to outside sources for this data

which is typically scattered about in the literature, and not readily

available.

As will be discussed below, the flexibility of the BCFM will be strongly

influenced by the software design in general, and the design of the userinterface module in particular.

3.6 The Structure of the Computer Code

The BCFM will include an overall code structure which will link together

the three major software modules: the user-interface module, the numerics

software module for solving the coupled equations, and the module of physics

subroutines which are the coded versions of these equations.

As with the other aspects of the BCFM code, the Harvard and NBS/Harvard

code development experiences of the last several years will be used as a basis

on which to build an improved framework for overall code structure. To

provide further guidance in this regard, a general review of other relevant

computer codes will be carried out. This will lead to useful ideas on BCFM

code structure optimization.

3.7 Guidelines for BCFM Flexibility

The design of the overall code structure and of the modules will be

influenced by guidelines for code flexibility. Flexibility in at least four

different areas is desirable.

- 14-
First is the capability to easily enrich the BCFM with new or revised

physics or numerics algorithms. Such flexibility will allow the code to be

conveniently used as a vehicle for testing such algorithms. It will also

allow revisions of the code to be conveniently prepared and published.

Second is the ability to select one from among a number of alternative

subroutines which describe a particular process. For example, the alternative

subroutines could be distinguished from one another by their degree of proven

reliability in a particular type of application. The selected subroutine

would then be used with the other subroutines which, together, would make up

an overall set of model equations for simulating a particular fire scenario

being studied. An example of this type of flexibility, already included in

the NBS/Harvard 5.2, is the ability to choose one from among several plume

dynamics subroutines [24].

The above-mentioned review of current numerics software literature will

likely reveal attractive and relevant options for BCFM numerics software. A

final type of flexibility involves the ability to test and/or implement such

alternative numerics software options in the numerics module of the code.

4. EXAMPLES OF THE ANTICIPATED USE OF THE BCFM

Three major uses of the BCFM can be anticipated: (1) calibration of

other zone-type models, an intended use; (2) calibration of the BCFM itself

against experimental fire data, an essential part of the BCFM development and,

therefore, an intended use; and (3) use of the BCFM as a (production)

engineering analysis tool, an inevitable result of the existence of the BCFM,

- 15 -
but a use distinct from the above two intended uses. In the present litigious

climate which surrounds issues of fire safety, these three uses inevitably

become tightly coupled.

The major use of the BCFM will be as a standard of reference against

which other models, with presumably fewer physical phenomena details, can be

evaluated. For example, in the evaluation of models designed to be economically executed in conjunction with CAD systems.

In many cases (e.g., for legal reasons) users of compartment fire models

may feel constrained to use only the "most complete" model available, and will

accept possible operational inconveniences of the BCFM in order to achieve

this.

Although no calibrations of one model against another more complete model

have been reported, there are several studies where simulations from different

fire models have been compared (e.g., [13-16] and [25]). While [25] does not

explicitly present comparative predictions of the models it considered, it

does discuss their physics; no conclusions are drawn, except by inference,

about the limits of model applicability.

Presumably the BCFM calibration of a candidate model would involve four

steps:

1. Defining the area of and limitations on the intended use of the

candidate model.

- 16-
2 . Defining the common use area, if any, between the candidate and the

BCFM.

3. Comparison of the models within their common use area(s). This could

involve analysis of the model structures, as in [25], as well as

comparative numerical results for a series of simulations.

4. Drawing conclusions from the results about the probable accuracy and

validity of the candidate model within its own intended use area.

Calibrations of fire models against experimental data already exist

(e.g., [1,25-28]). In these studies, data from a series of related experiments are compared with simulations. Conclusions are drawn about the

accuracy, validity and limitations of the simulations. These conclusions

extend to observations about physical effects not modeled or incompletely

treated whose inclusion or improvement would affect these particular simulations and the future, general use of the fire model. Published studies of

this type have been carried out by persons associated with the model development, and are based on experimental data developed within their own organizations. While the successful development of the BCFM will require comparisons

between calculations and experimental data, in order to minimize bias it is

not necessary, and may not be desirable, for final calibrations of the BCFM to

be carried out by its developers.

Fire models can also be used as tools of engineering analysis (e.g.,

[29-33]). They may be used as an adjunct to correlation and analysis of

experimental data [29,30]; to extrapolate from available data to situations

- 17 -
not tested [31]; or to predict fire performance of a building [30,32,33] so

that recommendations about facilities can be made during the building design.

While the BCFM might be used in this way, it is not one of its intended uses

in the sense of its being optimized for this purpose.

5. ACTIVITIES REQUIRED FOR MODEL DEVELOPMENT

In the above discussion, guidelines were presented for the development

and ultimate scope of the BCFM computer code. Development of the code will

require activities in four different areas:

1. the overall code structure;

2. the physical process algorithms and corresponding module of

subroutines, which will be published in the form of a readily

available and transportable catalog;

3. the numerics software module; and

4. the user interface module and user manual.

All of the above activities are planned for completion in approximately three

years

.

A significant portion of the work associated with the code development

and documentation, all activities except those of item 2, will involve a mix

of high level numerical analysis, computer science and structured programming.

- 18-
Complementing this software development activity will be the previously

described task of developing and improving the required physical process

algorithms and subroutines. This activity is fundamental to compartment fire

modeling research in that its products will be useful for model building

activities throughout the entire fire science community.

The development and improvement of physical process algorithm requires

significant manpower resources. It has been, and will continue to be carried

out by the CFMR Group, by other groups within CFR, and at institutions other

than NBS. The CFMR Group effort in this area is now entirely focused on items

delineated above in Section 3.3.3, The Appropriate Level of Modeling Detail

for the BCFM. The research outlined there will be completed in a time-frame

consistent with the approximately three years of the above-mentioned software

development. Advancements in algorithms and subroutines completed after this

time will be used to enrich, revise, or produce new generations of the BCFM.

Overall documentation for the BCFM will include a reference catalog of

all physical process algorithms and corresponding subroutines used. The

catalog itself will be transportable and usable in other compartment fire

model computer codes, and on commonly available computer hardware.

Preliminary development work on the algorithm/subroutine catalog has been

initiated, and a preliminary version of the catalog with recommendations on

the final product's style and format will soon appear [34],

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6. SHORT-TERM AND LONG-TERM OBJECTIVES

6.1 A Two-Stage Effort in Software Development

From initiation of BCFM software development work a three year effort

will be required before a final product is available. There is an immediate

and continuing need for a compartment fire model computer code with benchmarkquality features. It is this need which has motivated a two-stage effort in

the BCFM development program.

6.2 The First Stage Effort - Testing Ideas on a Prototype

One-Room Compartment Fire Model

The Harvard and NBS/Harvard codes were developed at Harvard University

through funding from the NBS/CFR Extramural Research Grant Program, and more

recently, at NBS/CFR where the development program was consolidated in 1983.

Since 1981, significant progress has been made as a result of the Harvard

University and NBS/CFR research efforts. This progress is manifested in the

various research/development versions of the codes. The most recent versions

of these codes, the single-room, "3.N" codes and the multi-room, "b.N" codes,

are the closest to benchmark quality of all compartment fire models now available. Except for one, these versions must all be considered to be developmental or research codes. The exception is the "official" Harvard 5 code,

which was completed and "fixed" in 1981 together with supporting documentation

[1]. Unfortunately, while this latter reference document provides a technical

description of the Harvard 5 code, it is not a user's manual, and no such

user's manual is available.

- 20-
There is a need to consolidate the advances which have been incorporated

into the NBS/Harvard 5.N codes; to publish an official, well-documented, high

quality, one-room NBS code; and to do this in a timely manner.

In response to the above need, a CFMR Group project has been established

to generate and publish such an official NBS code by the end of FY 1986. The

code will involve a consolidation of the capabilities of the Harvard-based

one-room codes. It will be supported by a user's manual and other appropriate

documentation. This project is considered to be a first-stage effort in the

development of the BCFM, in that it will involve the testing of BCFM ideas on

a prototype, one-room compartment fire model.

6.3 The Second Stage Effort - The BCFM

The major and second-stage BCFM software development effort described in

the bulk of this paper will be initiated during FY 1986. A development period

of approximately three years will lead to the first generation BCFM. It is

anticipated that the initial phases of this work will be carried out simultaneously with the latter part of the stage-one project, and that the time

interval of concurrent development will lead to mutual enhancements to the two

efforts

.

7 . SUMMARY

The Compartment Fire Modeling Research Group has been formed at the

Center for Fire Research of the National Bureau of Standards to develop a

zone-type Benchmark Compartment Fire Model (BCFM) computer code for simulat i n>-,

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compartment fire-generated phenomena. The purpose of this paper was to

describe the characteristics of this BCFM, and to outline the elements of a

program for its development.

Guidelines for the scope of this effort were presented in some detail.

These will provide guidance in the key areas of BCFM code development, which

include: bounds on the physical complexity of compartment spaces which the

BCFM will be capable of handling; limitations in the detail with which

individual compartment fire-driven processes will be treated in the overall

model; the type of numerics to be used for solving the governing BCFM

equations; the design of the computer code's user interface; the design of the

basic structure of the code; and the range of the code's flexibility within

its intended use as a standard of reference for other zone-type compartment

fire model codes, and as a vehicle for testing newly developed or improved

physical/chemical process algorithms.

Compatible with its established scope, specific activities required to

carry out BCFM code development have been outlined. These activities include

(1) the development of required new and improved physical/cheraical process

algorithms, and their corresponding subroutines which will lead to a transportable catalog of these algorithms and subroutines; and (2) the development of

overall software and its documentation. The latter activity will include the

software development associated with the code's numerics module, with the

user-interface module, and with the overall code structure.

The computer code under discussion will be unavailable for approximately

four years. For this reason, it cannot satisfy the immediate and continuous

- 22 -
need for a well-documented, state-of-the-art, compartment fire model computer

code with benchmark-quality features. In response to this need, a project to

generate and publish such an official NBS one-room code in approximately one

year has been initiated recently. The code will mainly be the result of a

consolidation of many of the recent advances embodied in the NBS/Harvard 5.N

and 6.N research/developraent codes. This project is considered to be a firststage effort in the development of the BCFM, in that it will involve the

testing of BCFM ideas on a prototype, one-room compartment fire model.

The development of the BCFM computer code which is the subject of this

paper can be thought of as the next major step within the progressive development of benchmark compartment fire model computer codes. Although outside the

scope of present planning, it is clear from Emmon's prophecy of reference [19]

that future advances in fire science and technology will eventually render

even this BCFM obsolete, thereby leading to the requirement for yet another

generation BCFM.

8. REFERENCES

[1]

Mitler, H.E. and Emmons, H.W., Documentation for CFC V, The Fifth

Harvard Computer Fire Code, Harvard University Report to U.S. National

Bureau of Standards, NBS-GCR-81-344 , 1981.

[2] Gahm, J.B., Computer Fire Code VI - Volumes 1 and 2, Harvard University

Report to U.S. National Bureau of Standards, NBS-GCR-83-45 1 , 1983.

[3] Mitler, H.E., The Harvard Fire Model, Fire Safety Journal, 9^ (1985) 7.

[4] Rockett, J. A. and Morita, M., The NBS/Harvard VI Multi-Room Fire

Simulator, to appear as a U.S. National Bureau of Standards NBSIR.

[5] Siu, N.O., COMPBRN - A Computer Code for Modeling Compartment Fires,

UCLA Report UCLA-ENG-8257 (1982) and U.S. Nuclear Regulatory Commission

Report NUREG/CR-3239 (1983).

- 23 -
[6]

Siu, N.O., Physical Models for Compartment Fires, Reliability

Engineering, 3_ (1982) 229.

[7] Siu, N.O., Probabilistic Models for the Behavior of Compartment Fires,

U.S. Nuclear Regulatory Commission Report NUREG/CR-2269 (1981).

[8] Jones, W.A., A Model for the Transport of Fire, Smoke and Toxic Gases

(FAST), U.S. National Bureau of Standards Report NBSIR 84-2934 (1984).

[9] Tanaka, T., A Model of Multiroom Fire Spread, U.S. National Bureau of

Standards Report NBSIR 83-2718 (1983).

[10] Pape, R. , Waterman, T.E. and Eichler, T.E., Development of a Fire in a Room from Ignition to Full Room Involvement - RFIRES, IIT Research

Institute Report, IITRI Project J6485, October 1980.

[11] MacArthur, C.D., Dayton Aircraft Cabin Fire Model - Version 3:Vol 1 - Physical Description, University of Dayton Research Institute, May 1981.

[12] Yang, K.T. and Liu, V.K., UNDSAFE-II: A Computer Code for Buoyant

Turbulent Flow in an Enclosure with Thermal Radiation, University of

Notre Dame Report TR-79002-78-3, July 1978.

[13] Parikh, J.S., et al., Survey of the State-of-the-Art of Mathematical

Fire Modeling, Underwriters Laboratories Report File NC 554 (1983).

[14] Friedman, R. , Status of Mathematical Modeling of Fires, Factory Mutual

Research Corp. Report RC 81-BT-5 (1981).

[15] Emmons, H.W., MacArthur, C.D. and Pape, R. , The Status of Fire Modeling

in the U.S., paper presented at the U.S. -Japan Panel on Fire Research

(1979).

[16] Hathaway, W.T., Survey on Fire Modeling Efforts with Application to

Transportation Vehicles, U.S. Department of Transportation Report

D0T-TSC-0ST-8 1 -4 (1981).

[17] Cooper, L.Y., Smoke Movement in Rooms of Fire Involvement and Adjacent

Spaces, Fire Safety Journal, 1_ (1984) 33.

[18] Cooper, L.Y. and Nelson, H.E., Life Safety through Designed Safe

Egress - A Framework for Research, Development, and Implementation, 6th

Meeting UJNR Panel on Fire Research and Safety, Tokyo, 1982.

[19] Emmons, H.W., The Future History of Fire Science, Combustion Science and

Technology, (1984) 167.

[20] Gear, C.W. , Simultaneous Numerical Solution of Differential-Algebraic

Equations, IEEE-CT-18, J_ (1971).

[21] O'Leary, D. , U.S. National Bureau of Standards, private communication,

1984.

- 24 -
[22] Rarasdell, J.D., Variable Elimination in Home Fire Code, ASME Paper

81-HT3, 20th ASME/AIChE National Heat Transfer Conference, Milwaukee,

1981.

[23] Rockett, J.A., Data for Room Fire Models, Combustion Science and

Technology, (1984) 137.

[24] Rockett, J.A., A Comparison of Plume Entrainment Models, to appear as a U.S. National Bureau of Standards NBSIR.

[25] Jones, W.A., A Review of Compartment Fire Models, U.S. National Bureau

of Standards Report NBSIR 83-2684 (1983).

[26] Rockett, J.A., Modeling of NBS Mattress Tests with the Harvard Mark V

Fire Simulation, Fire and Materials, 6_ (1982).

[27] Morita, M. , Rockett, J.A. and Cooper, L.Y., Experience with the

NBS/Harvard Mark VI Fire Simulation, to appear as a U.S. National Bureau

of Standards NBSIR.

[28] Cooper, L.Y., A Mathematical Model for Estimating Available Safe Egress

Time in Fires, Fire and Material, 6_ (1982) 135.

[29] Quintiere, J.G. and McCaffrey, B.J., The Burning of Wood and Plastic

Cribs in an Enclosure - Volume 1, U.S. National Bureau of Standards

NBSIR 80-2054, November 1980.

[30] Cooper, L.Y. and Stroup, D.W., ASET - A Computer Program for Calculating

Available Safe Egress Time, Fire Safety Journal, 9_ (1985) 29.

[31] Rockett, J.A., Park Service Room Fire Test Simulations Using the Harvard

Level 5.2 Computer Fire Model, U.S. National Bureau of Standards NBSIR

83-2805, June 1984.

[32] McCaffrey, B.J., Rockett, J.A. and Levine, R.S., Naval Fire Fighting

Trainer - Effect of Ventilation on Fire Environment (Modeling

Calculations for 19F3 FFT), to appear as U.S. National Bureau of

Standards NBSIR.

[33] Cooper, L.Y., The Development of Hazardous Conditions in Enclosures with

Growing Fires, Combustion Science and Technology, 33_ (1983) 279.

[34] Stroup, D.W., The Establishment of a Catalog of Compartment Fire

Submodel Algorithms and Associated Computer Subroutines, to appear as U.S. National Bureau of Standards NBSIR.

-25-
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR-85/3252

2. Performing Organ. Report No 3. Publication Date October 1985

4. TITLE AND SUBTITLE

A Program for the Development of a Benchmark Compartment Fire Model Computer Code

5. AUTHOR(S)

Leonard Y. Cooper, John A. Rockett, Henri E. Mitler and David W. Stroup

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

Gaithersburg, MD 20899

7. Contract/Grant No.

8 . Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

10.

SUPPLEMENTARY NOTES

] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

With a variety of objectives in mind, many different compartment fire

model computer codes have been developed within the fire safety/research

community. Yet, no one of these can be described as being a "benchmark"

model in the sense that it is reliable enough to be accepted as a standard

of reference for the performance of design-oriented fire models. It is

the major objective of the Compartment Fire Modeling Research (CFMR)

Group in the Fire Safety Technology Division of the Center for Fire

Research (CFR) to develop such a Benchmark Compartment Fire Model (BCFM)

computer code. This paper describes the characteristics of this BCFM,

and outlines the program which will lead to its development.

12.

KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words by semicolons)

compartment fires; computer programs; fire models; fire research; room fires

13. AVAILABILITY

Unlimited

| | For Official Distribution. Do Not Release to NTIS

[ J Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

fX] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

29

15. Price $9.95

USCOMM-DC 6043-P80