interactive web based risk assessment system.pdf

7/31/2019 interactive web based risk assessment system.pdf

1/56

n v ua nqu ry em nars

I NTERACTI VE WEB

BASED RI SK

ASSESSMENT SYSTEM

By: KIEN TRAN

Department of Chemical EngineeringThe University of Queensland

Supervisor: ASSOCIATED PROFESSOR IAN CAMERON

Date: 27TH

OCTOBER 2000


2/56

55 Beams Rd

Boondall

Qld 4034

27th

October 2000

The Executive Dean

Faculty of Engineering, Physical Sciences and Architecture

The University of Queensland

St Lucia

Qld 4072

Dear Sir,

I hereby submit for consideration my Individual Inquiry entitled:

Interactive Web-based Risk Assessment System

in partial fulfillment of the Bachelor of Engineering (Chemical) Honours degree

for which I have been studying. To the best of my knowledge all the work

presented is original except where otherwise acknowledged.

Yours Sincerely,

Kien Tran


3/56

-

Acknowledgements

I wish to take this opportunity to say a big thankyou to the following people

for their continuous inputs and support throughout the course of this Individual

Inquiry. The work presented in this Individual Inquiry could never have been

accomplished so smoothly without the help and support from these people.

To my Individual Inquiry supervisor, Associated Professor Ian Cameron for his

invaluable advice and input to the modeling aspect and the models implemented

during the course of this work.

And to my great friend, Ben Wong for passing on the knowledge he gained

from previous work on the HEVAN project. Many parts of the work presented

in this Individual Inquiry could not have been attained without his knowledge

and experience with the operation of the HEVAN calculation engine.

Again, I like to express all my gratitude for these two extraordinary people for

helping me through the course of the Individual Inquiry.


4/56

-

Abst rac t

The Hazard EVent ANalysis package or HEVAN was created as an interactive

Web based risk assessment tool to assist town planners and process engineers in

design involving storing, handling and transportation of hazardous chemicals.

The main feature of HEVAN is the set of detailed analysis models, which allow

users to predict the physical effects of major hazards such as release of

dangerous chemicals, fire radiation and explosion.

The objectives of the Individual Inquiry are to complete the set of detailed

analysis models of the HEVAN package and to revise the structure of HEVAN

to make it easier to use.

The Individual Inquiry required a lot of knowledge beyond the normal Chemical

Engineering curriculum, particularly computer and Internet programming. A

substantial amount of time was devoted to the study of these areas in order to

implement new models successfully.

Five new models were successfully added to the current collection of detailed

analysis models of the HEVAN package. The material property database had

been upgraded to include up to 36 components. The general structure of

HEVAN had also been revised.


5/56

-

TABLE OF CONTENTSACKNOWLEDGEMENTS______________________________________________I

ABSTRACT_________________________________________________________ II

TABLE OF CONTENTS _____________________________________________ III

LIST OF TABLES __________________________________________________ IV

LIST OF FIGURES _________________________________________________ IV

1.0 INTRODUCTION________________________________________________ 1

1.1 The Hazardous EVent ANalysis (HEVAN) Package _______________________ 1

1.2 Thesis Objectives ____________________________________________________3

2.0 LITERATURE REVIEW __________________________________________ 4

2.1 Risk Management ___________________________________________________ 42.1.1 Consequence Analysis Models__________________________________________5

2.2 The Internet ________________________________________________________8

2.2.1 The World Wide Web (WWW) __________________________________________92.2.2 HyperText Markup Language (HTML)____________________________________92.2.3 CGI Programming_____________________________________________________9

3.0 APPROACH ___________________________________________________ 10

4.0 THE DETAILED ANALYSIS MODELS ____________________________ 11

4.1 HEVAN Operating Structure_________________________________________ 11

Program __________________________________________________________ 11

4.2 How the Detailed Analysis Models are Set Up ___________________________12

4.3 How the Detailed Analysis Model Work ________________________________13

4.4 Implementation of Models ___________________________________________ 15

4.5 Debugging_________________________________________________________ 16

5.0 PROGRESS MADE TO HEVAN __________________________________ 17

5.1 Validating the Models _______________________________________________ 175.1.1 Thermal Radiation from a Rectangular Pool Fire__________________________185.1.1 Dispersion of Gas from a Continuous Area Source________________________195.1.2 Continuous Point Source Dispersion Contours ___________________________21

6.0 DISCUSSION __________________________________________________ 23

7.0 RECOMMENDATION FOR FURTHER WORKS ____________________ 24

8.0 CONCLUSION _________________________________________________ 259.0 REFERENCES_________________________________________________ 26

APPENDIX 1 ______________________________________________________ 27

APPENDIX 2 ______________________________________________________ 29

APPENDIX 3 ______________________________________________________ 32

APPENDIX 4 ______________________________________________________ 36

GLOSSARY________________________________________________________ 50


6/56

-

List of Tables

Table 4-1 Summary of Program Functions .............................................................11

Table 4-2 Content of HEVAN Sub-directories........................................................12

Table 4-3 Common Errors and their Causes............................................................16

Table 5-1 Inputs for Thermal Radiation from a Pool Fire model .............................19

Table 5-2 Inputs for Dispersion of Gas from a continuous area source model .........20

Table 5-3 Inputs for Continuous point source dispersion contours model................22

Lis t o f F igu re s

Figure 1-1 Screenshot of HEVAN starting page .......................................................2

Figure 2-1 Effect and Vulnerability Models..............................................................5

Figure 4-1 Diagram of How the detailed analysis model work................................13

Figure 5-1 Plot of Thermal Radiation from a Pool Fire...........................................18

Figure 5-2 Plot of Dispersion of Gas from a continuous area source.......................20

Figure 5-3 Plot of Continuous point source dispersion contours..............................21


7/56

-

1.0 INTRODUCTION

Every operational activity associated with chemicals always carries an

elemental of risk of hazards occurring. The effects of such chemical hazards can

be devastating: facilities can be destroyed, the environment can be harmed and

lives can be lost. That is why it is essential to have models available for

assessing the physical effects of accidental releases of hazardous chemicals.

The Internet has come a long way since its beginning in the 1960s. The Internet

has emerged as a powerful medium for communication and transfer of

information. It is continually growing and is expected to accelerate at greater

speed year by year in the future. The Internet therefore offers a great potential

for important applications such as risk assessment tools for chemical hazards.Hence the Hazardous EVent ANalysis package or HEVAN was created to take

advantage of the Internet promising capabilities.

The main benefit arising from the use of the Internet is the speed and ease of

upgrading. For all existing risk management software on the market, a new

upgrade package has to be produced and distributed to the customers whenever

a new upgrade is made. This process can be very tedious and time consuming.

However if the risk management package is Internet based, only the online

package has to be upgraded for every customer to have access to the new

features. The new package can be access any time given the customer has access

to the Internet.

1.1 The Hazardous EVent ANalysis (HEVAN) Package

The Hazardous EVent ANalysis package or HEVAN is a Web-based interactive

risk assessment system, which provides supports for decision making into land-use planning issues relating to operations involving dangerous substances. This

project is a joint effort between the Brisbane City Council, Logan City Council,

Caltex and the University of Queensland Chemical Engineering Department.

The project has been developed for several years and ongoing refinement and

upgrade are continually made to improve the package.


8/56

-

The complete HEVAN Web site will contain:

Information and resources for the identification, analysis and

management of risks concerned with hazardous substances.

Detailed analysis models to predict the impact of a range of different

hazard events and incidents.

Decision support for the design and operation of facilities handling

hazardous substances and the transportation of such substances.

References to International and Australian regulations and standards

related to hazardous substances.

Strategic links to other related Web sites on the Internet.

A screenshot of the front page of the HEVAN Web site is shown in Figure 1-1.

Figure 1-1 Screenshot of HEVAN starting page


9/56

-

Some other important potentials of HEVAN apart from assisting town planners

and engineers in process safety design are:

In emergency response situation where the emergency team must

determined the danger zone around the hazard site

Use as an educational tool for risk management

Commercial prospects where a password entry system is applied

1.2 Thesis Objectives

The objectives of this Individual Inquiry are:

To complete the collection of detailed analysis models of theHEVAN package

To revise the structure of HEVAN Web site to make it user-friendly

The goal for the completion of this Individual Inquiry was to have HEVANdeveloped to a stage where it could be used for the purpose it designed for.


10/56

-

2.0 LITERATURE REVIEW

This section looks at information relating to this Individual Inquiry. This

Individual Inquiry required a reasonable amount of proficiency in each of the

following area:

Modelling

Internet

HTML

C programming

UNIX operating system

The last three parts of the above are not part of the normal Chemical

Engineering curriculum, hence a substantial amount of time of the IndividualInquiry were devoted in researching and learning these areas.

2.1 Risk Management

Risk management is an important field of the process industry aimed at reducing

the risk of hazards occurring. To understand risk management one must know

the definitions of risk management, hazard and risk.

RISK MANAGEMENT is the systematic application of policies, practices, and

resources to the assessment and control of risk affecting human health and

safety and the environment. Hazard, risk, and cost/benefit analysis are used to

support development of risk reduction options, program objectives, and

prioritization of issues and resources. A critical role of the safety regulator is to

identify activities involving significant risk and to establish an acceptable level

of risk. Near zero risk can be very costly and in most cases is not achievable [1].

HAZARD is the inherent characteristic of a material, condition, or activity that

has the potential to cause harm to people, property, or the environment [1].

RISK is the combination of the likelihood and the consequence of a specified

hazard being realized. It is a measure of harm or loss associated with an activity

[1].


11/56

-

2.1.1 Consequence Analysis Models

There are two main types of consequence analysis models employed in risk

management to determine the effects of hazards. These are effect and

vulnerability models. The effect models used mathematical models to predict

the effects of hazard events in term of measurable quantities, such as

concentration of toxic gases, radiation levels from fires or pressures from

explosions. The vulnerability models concentrated on the impact on resources,

such as people, facilities and the environment. The relationship between these

types of models and how they are applied are illustrated in Figure 2-1.

Figure 2-1 Effect and Vulnerability Models (adapted from [2])

The set of detailed analysis models of the HEVAN package is effect models.

They are used to predict the effects of four major classes of hazard events:

Releases

Fire radiation

Dispersion

Explosion

EFFECTMODELS

ENVIRONMENT

VULNERABILITYMODELS

Physical Effectsfrom

Physical Phenomena

Calculated Damageto

Resource

EFFECT AND VULNERABILITY

MODELS


12/56

-

2.1.1.1ReleasesThe release models are used to estimate the outflow of liquids and gases

escaping from ruptured vessel or pipe. There are seven models listed under this

section in the HEVAN Web site:

1. Gas Outflow from Vessel

2. Gas Outflow from a Pipe

3. Liquid Outflow from Vessel

4. Liquid Outflow from a Pipe

5. Liquefied Gas Outflow from Vessel

6. Liquefied Gas Outflow from a Pipe

7. Initial Flash Fraction of Superheated Liquid

Of these seven models only five (1,2,3,5,7) were implemented at the start of this

Individual Inquiry.

2.1.1.2Fire RadiationThe fire radiation models are used to estimate the heat load radiated from a fire

event at an object. There are three models listed under this category in HEVAN:

1. Thermal Radiation from a BLEVE

2. Thermal Radiation from a Flare

3. Thermal Radiation from a Pool Fire

Of these three models only the first two were implemented at the start of this

Individual Inquiry.

2.1.1.3DispersionThe dispersion models are used to estimate the spread of gases and vapours to

the environment due to turbulent airflow. The dispersion models employed by

HEVAN are based on the Gaussian plume models, which are derived from the

Gaussian distribution. There are four models listed under this category in

HEVAN:


13/56

-

1. Dispersion of Gas from a Continuous Point Source

2. Dispersion of Gas from a Continuous Area Source

3. Continuous Point Source Dispersion Contours

4. Dispersion from an Instantaneous Source (Puff)

Of these four models only two (1,4) were implemented at the beginning of this

Individual Inquiry.

2.1.1.4ExplosionThe explosion models are used to estimate the impact of vapour cloud explosion

where a cloud of explosive vapour or gas is ignited causing a shock wave. There

are three models listed in this category of HEVAN:

1. Vapour Cloud Explosion (TNO Shock Wave)

2. Vapour Cloud Explosion (TNO Correlation)

3. Vapour Cloud Explosion (TNT Equivalence)

All three models had been implemented at the start of this Individual Inquiry.

2.1.1.5IncidentsIncidents are chains of events occurring in consecutive order. For example, gas

released from a ruptured pipe can lead to a dispersion event, upon on ignition

can lead to a flash fire or vapour cloud explosion. There are three models listed

under this category in HEVAN:

1. BLEVE Scenario (Fireball + First Degree Burns)

2. BLEVE Scenario (Fireball + Second Degree Burns)

3. BLEVE Scenario (Fireball + Fatal Burns)

Only the first of these three models was implemented at the start of this

Individual Inquiry.


14/56

-

2.2 The Internet

In the late 1960s, the ARPA, a division of the US Department of Defense

began developing a network called the ARPANET. This network was aimed to

allow the US authorities to communicate and maintain control of their missiles

even after a nuclear strike. Over the years, the ARPANET has evolved into the

Internet of today through cooperative research amongst the academic

communities. The biggest potential of the Internet was the unlimited power to

communicate and exchange information from anywhere in the world, given one

has access to the Internet via either a phone line or a local network.

The Internet is global computer network interconnecting numerous computer

networks [4]. A set of common protocols called Transmission Control Protocol/

Internet Protocol (TCP/IP) is used to connect the networks together on the

Internet. These protocols determine how computers communicate with each

other.

Some important functions developed for today Internet were:

Sending and receiving electronic mail (e-mail)

Transferring files between computers (FTP)

Reading and posting messages on electronic message boards Internet chatting and live video conferencing

The Internet has experiencing a phenomenon growth rate over the years and will

continue to grow at breakneck speed in the future as more access and awareness

reach the general population. Almost all organisations in the world today have

regconised the great commercial potential of the Internet and has already began

exploiting this potential. This was clearly demonstrated by the increasing

number of commercial Web sites on the Internet, especially Internet shopping

sites. Hence, the implementation of important technologies such as simulation

engines or risk management software online would be a logical step for many

organisations to take advantage of the growing exposure of the Internet to the

general public markets. However, there are very few Web sites found on the

Internet that contains similar features as HEVAN.


15/56

-

2.2.1 The World Wide Web (WWW)

The core of the Internet is the World Wide Web, which is an information system

interconnected together by hypertext links of Web pages. Web pages are

documents that can contain text, images, audio and video. Each Web page can

have several hypertexts linking it to other pages thus forming a Web of

information. The Web can be surf through any type of Internet browsers with

the most common ones used are Netscape Navigator and Microsoft Internet

Explorer.

As HEVAN is a Web-based package it can be accessed via the World Wide

Web.

2.2.2 HyperText Markup Language (HTML)

Hypertext Markup Language or HTML is a simple programming language

derived from SGML (Standard Generalised Markup Language), which is used

to create Web pages. HTML uses a set of tags, similar to the way Microsoft

Word uses Styles to describe the elements inside a Web page such as headings,

paragraphs and lists. Due to its simplicity, HTML can be written using any

simple text-editing program such as Notepad or more advanced HTML editor

such as Microsoft Frontpage. A sample HTML page of the HEVAN package is

included in the Appendix for illustration purposes.

2.2.3 CGI Programming

Common Gateway Interface or CGI is a method of allowing programs on a Web

server to be run by using data sent from a browser [3]. CGI is used to run the

detailed analysis models of HEVAN via the data sent from the HTML input

pages. It is then use to generate an output Web page of the result dynamically

and send it back to the user on the Net. The CGI scripts can be written in any

computer programming language, such as Perl, C or Java as long as the server

supports it. The CGI script of HEVAN was written in C language.


16/56

-

3.0 APPROACH

The general approach used to carry out this Individual Inquiry is:

1. Research acquired knowledge to carry out the Individual Inquiry

Acquired proficiency in C and HTML programming

Familiarisation with the UNIX operating system

2. Understand understand how the model in HEVAN works

Analysing the source code for all the files to work out how each

file work and how they are related with each other

3. Prepare prepare the models for implementation

Research through various modeling books to develop the best

models

Develop a general calculation algorithm for each of the models to

be implemented

4. Implement implement models to the collection Create the new models using C/C++ language and add them to

the main calculation program

5. Verify check to see if the models operated correctly

The majority of time spent on this Individual Inquiry was devoted to the first

two steps since C and HTML programming is a relative new area to me. I have

never programmed in either C or HTML language before except Matlab. Hence

a good portion of the project was used in researching and learning these new

areas. The programming aspects were achieved through reading and applying

many exercises and tutorials from several basic C and HTML introduction

books. Frequent meetings with my predecessor on this project, Mr. Ben Wong

and my supervisor, Assoc. Prof. Ian Cameron also sped up my learning curve in

C and HTML programming.

The remaining three steps were achieved with a much better progress as I am

already familiar with the area of modeling through the various modeling

subjects undertaken in my undergraduate curriculum. The knowledge gained

from the first two steps also accelerated the implementation and verification

process. Common troubles arises from this process were resolved from regular

consultations with Mr. Wong and Dr. Cameron.


17/56

-

4.0 THE DETAILED ANALYSIS MODELS

This section looks at the structure of the HEVAN package, how the detailed

analysis models are setup and how they work. The detailed analysis models are

the most important part of the HEVAN package. These models are taken fromthe book, Methods for the Calculations of Physical Effects, published by TNO

(The Netherlands Organisation of Applied Scientific Research) [7] [8].

4.1 HEVAN Operating Structure

As discussed earlier, the HEVAN Web site uses a CGI script to power the

detailed analysis models in its interactive library of models. The CGI script use

three programs to do this:

1. Hevancal the main and most important program of HEVAN

This program determines the type of model to be performed, run the

calculation and generate the output data before sending it to the

plotting program.

2. GNUPlot the plotting program employed hevancal

This is a popular plotting program for the UNIX system, which is

used by hevancal to plot the output data from the model calculationengine.

3. Ppmtogif a image converting program

As the image generated by GNUPlot is in portable bitmap (PBM)

format it cannot be shown on the Web, hence ppmtogif is used to

convert this image to the more standard format, GIF.

The functions of each program are summarised in Table 4-1.

Table 4-1 Summary of Program Functions (adapted from [3])

Program Description Functions

test.cgi The CGI script which allow

users run hevancal by entering

the data via a Web browser

Processing data send from the

Internet

Creating input file for hevancal


18/56

-

Running server based programs:

hevancal, gnuplot and ppmtogif

Making and returning the Web

page containing the results

Hevancal The main program behind the

detailed analysis models

Determine the type of data

receive in the input page

Determine which type of

calculation to perform

Carry out the calculations

Create data file and command

files for gnuplot

Create Web page of message

given by hevancal during

execution

Gnuplot A UNIX plotting program Plot the data receive for hevancal

Create a PBM image file of plot

Ppmtogif An image conversion program Convert the PBM image file to a

more standard file format, GIF

4.2 How the Detailed Analysis Models are Set Up

The HEVAN package resides inside the Computer Aided Process Engineering

(CAPE) Web server, Daisy, which run UNIX as its operating system. Each of

the detailed analysis models comprised of three files: an HTML template, an

input template and a source file for calculations. All of these files and other

main programs are stored inside the directory /www/www/hevan in Daisy. The

details of this folder are summarised in Table 4-2.

Table 4-2 Contents of HEVAN directories

Directory Contents

Bin Hevancal program

test.cgi CGI scripts

Calc Source files for hevancal


19/56

-

Effects Model HTML forms

Model input template

Tmp Plot data files

Plot command files

Plots produced

Hevancal message HTML pages

4.3 How the Detailed Analysis Model Work

The process in which HEVAN operate the detailed analysis models on the Web

is quite complex. This section gives a brief description of how HEVAN carry

out the operation of running a model using inputs received from the user on the

Web. The overall sequence of events is summarised in Figure 4-1.


20/56

-

Figure 4-1 Diagram of How the Detailed Analysis Models Work (adapted

from [3])

From Figure 4-1, the operation sequence of HEVAN is described as follow:

1. The user selected a model from the collection and enters theappropriate required input. The most important inputs are the X

value, which defined the range of the X axis to be plot and the P

value/s, which defined the parameter of interest to be held constant.

2. The CGI script take the inputs from the selected model HTML page

specified by the user and put into an input file called hevancal.inp,

which then pass to the main calculation program, hevancal.

template file

test.cgiCGI script

hevancal.inp(input file)

hevancal

gnuplot.dat(data file

gnuplot.gnu(command file)

gnu plot

plot image(PBM)

ppmtogif

Server - Daisy

plot image(GIF)

message(HTML file)

User's Web

Browser

Client - User's Computer

code for plot Web page (6)

data inputs (1)

(2)

(2)

(3)

(3) (3)

(4) (4)

(4)

(5)

(5)

program

file

data transfer overInternet

data transfer withincomputer

links


21/56

-

3. Hevancal then process the inputs from hevancal.inp to determine

which model calculation module to be used and run the calculations.

It then generates the output files for plotting, gnuplot.dat and

gnuplot.gnu and an HTML file for the plot image

4. The program gnuplot is then called to plot the data and create the

bitmap plot image

5. The PBM image is then convert to a GIF image using ppmtogif.

6. Concurrently the CGI script takes the HTML messages and the GIF

plot image and transform into a Web page and send it back to the

user.

4.4 Implementation of Models

The procedure of implementing new models to the existing collection is very

simple. The process is described as follow:

1. Create a calculation module and appropriate template files (HTML

and inp) for the new model. Some additional calculation modules

may require to be added to other main program for special

calculations. For example, new view factor function has to be added

to the existing collection of view factor calculation modules before it

can used by any model.

2. Place the new files to the appropriate directory in HEVAN i.e. the

source code to the calc directory and the template files to the effects

directory.

3. Edit the main calculation files, hevancal.h and calcs.cpp to

regconised the new model.

4. Edit the file Makefile to enable the new model (*.cpp) file to make

into an object file (*.o).5. Make the new hevancal program.

6. Copy the new hevancal program to the bin directory.


22/56

-

4.5 Debugging

Errors are often occurred when a new model implemented to the HEVAN

package. These errors ranging from minor typing errors to the extent where

some or most part of the calculation module to be rewritten. The process of

resolving these errors is called debugging. There are many bugs encountered

throughout the progress of this Individual Inquiry and some common errors are

summarised in Table 4-3 below.

Table 4-3 Common Errors and their Causes

Bugs Possible Causes

Hevancal output return the message

unknown event in hevancal output

Event name specified in template file

doesnt correspond with any event

name in hevancal

The calculation module has not been

compile into hevancal yet

Plot from model does not appear Invalid input data

Plot from other model appear Hevancal fail to complete the

calculations calculation module

failure

Event name specified does not

corresponded with any event name in

hevancal

Web browser returns message unable to

find ?.inp

Template file is missing or incorrectly

name

The above errors are the most common ones encountered during the course of

the Individual Inquiry. The error associated with no output plot is the most

difficult one to debug since a complete review the calculation module is

required in order to fix the error. A large portion of the Individual Inquiry was

devoted to debugging.


23/56

-

5.0 PROGRESS MADE TO HEVAN

There were a lot of progresses made at the completion of the Individual Inquiry

to improve the HEVAN package. The improvements are summarised as follow.

Successful implementation of the following models:

Thermal radiation from a rectangular/circular pool fire

Dispersion from a continuous area source

Continuous point source dispersion contours

Dispersion from an instantaneous source (puff)

Vapour cloud explosion (TNT Equivalent)

Note: most of the above model calculation modules had been pre-written but has

yet to be implement or need refinement.

The material property database was upgraded from five components to 36

components.

The material selection list for each model was revised to include only

substances of relevant interest.

Some Web pages were fixed up for spelling mistakes and/or to include extra

parameters required by the models.

However, there is still a lot of work to be done to improve the HEVAN package

but this requires time.

5.1 Validating the Models

The most important part of modeling was validation. This process is used to

check how well the models describe the phenomenon it was developed for.

There is no correct model to any phenomenon, just the best one. Three methods

were employed in validating the new models implemented to the HEVAN Web

sites:


24/56

-

1. Check to see whether the displayed results showed the expected

relationship between the plotting variables.

2. Perform sensitivity analysis test to determine the range of the models

3. Compare the values calculated by the models with literature values.

The following summarised the results for each model implemented.

5.1.1 Thermal Radiation from a Rectangular Pool Fire

In this model, the pool fire is considered as a radiator with a finite surface (the

visible part of the flame) and an average radiation emittance (E) which is

determined by the flame temperature, which depends on the burning material

[7]. The heat radiation load is proportional to E and depends on the dimension

of the radiator and on the distance to this radiator; these geometric parameters

are jointly expressed in the form of so-called view factor (F). Figure 5-1 shows

a plotted generated by the inputs in Table 6-1. The shape of the curves is correct

as the heat load decreases with increasing distance from the fire source. The

heat load values changes accordingly to any input changes. Some values

calculated by this model seems to correlate well with literature values. There are

still some refinements to be made to improve this model.

Figure 5-1 Plot of Thermal Radiation from a Rectangular Pool Fire


25/56

-

Table 5-1 Inputs for the Thermal Radiation from a Rectangular Pool Fire

Plot

Input Name Input Value

Material Benzene

Carbon to Hydrogen ratio of Fuel 1.0

Mass Burning Rate (kg/m2.s) P 0.05 0.10 0.15

Length of Pool (m) 10

Width of Pool (m) 10

Distance between Object and Edge of

Pool (m)

X 20 to 100

Height to Tank Top (m) 0

Relative Humidity (%) 70

Ambient Temperature (deg C) 25

Wind Speed (m/s) 5

Emittance of Clear Flame (kW/m2) 120

Emittance of Smokey Flame (kW/m2) 40

5.1.1 Dispersion of Gas from a Continuous Area Source

The dispersion model is based on the Gaussian plume model, which is derivedfrom the Gaussian distribution. Figure 5-2 shows a plot generated from the

inputs given in Table 5-2. The dispersion concentration decreased accordingly

of the dispersion distance as expected. The model responded well to changes in

inputs. The values calculated by the model seem to be of correct magnitude.


26/56

-

Figure 5-2 Plot of Dispersion of Gas from a Continuous Area

Source

Table 5-2 Inputs for the Dispersion of Gas from a Continuous Area

Source Plot

Input Name Input ValueOutflow Rate (kg/s) P 10

Roughness Factor Flat Land

Pasquill Stability Class D Neutral

Wind velocity at 10m height (m/s) 5

Concentration Averaging Time (min) 10

Release Height of Gas (m) 10

Height of Plume (m) 0

Width of Plume (m) 0

Length of Plume (m) 0

Downwind distance (X coordinate) X 100 to 1000

Downwind distance (Y coordinate) 0

Downwind distance (Z coordinate) 0

Number of Summation 3


27/56

-

5.1.2 Continuous Point Source Dispersion Contours

In order to obtain an idea of the surface area in which the concentration is

higher than a prescribed value, a concentration contour can be calculated. This

model calculated the dispersion contours of a continuous point source. Figure 5-

3 shows a plot generated from the inputs given in Table 5-3. As shown, the plot

only gives half of the contour since the contour is symmetrical in shape. There

is a minor error with the plot since it kept on plotting after the lateral distance

reaches zero. The main hevancal program needs to be modified to fix this minor

problem.

Figure 5-3 Plot of Continuous Point Source Dispersion Contours


28/56

-

Table 5-3 Inputs for the Continuous Point Source Dispersion Contours

Plot

Input Name Input Value

Downwind distance (X coordinate) X 50 to 1000

Concentration of interest (mg/m3) P 100 200 500

Outflow rate (kg/s) 3

Roughness factor Residential Land

Pasquill Stability Class D Neutral

Wind velocity at 10m height (m/s) 5

Concentration Averaging Time (min) 10

Release height of gas (m) 5

Height of Plume (m) 0

Width of Plume (m) 0


29/56

-

6.0 DISCUSSION

The goal for the completion of the Individual Inquiry was to develop HEVAN

up to stage where it can be used for the purpose it designs for. There was a great

amount of work set for the Individual Inquiry in order to achieve this goal. Themajority of works were to complete the set of detailed analysis models and to

restructure the Web site to make it user-friendly.

The set of detailed analysis models were nearly complete except for two outflow

models, Liquid Outflow from a Pipe and Liquefied Gas Outflow from a Pipe,

which will required substantial amount of work to complete. The reason for the

incompletion of the set of detailed analysis models was a lot of knowledge

required was outside the normal Chemical Engineering curriculum. Hence a

substantial amount of time was devoted in gaining proficiency in these fields.

And the original documentation, especially the source codes for calculation

modules were not detailed enough.

The restructuring of the HEVAN Web site was done using the expertise of my

predecessor, Mr. Ben Wong. The Web site was restructured in such a way to

achieve a consistency in page format and layout. It is a lot more comprehensive

and user-friendly.


30/56

-

7.0 RECOMMENDATIONS

There were a good amount of efforts made during the completion of the

Individual Inquiry to continue the development of the HEVAN package. There

is still a lot of work to be done to complete the set of detailed analysis models,however. There are incomplete models to implement and refinement work needs

to be done to improve existing operable models. Some of these refinement

works are discussed in the following.

The first and foremost task is to complete the set of detailed analysis models.

The models need to be implemented are: Liquid Outflow from Pipe, Liquefied

Outflow from Pipe, BLEVE Scenario (Fireball + Second Degree Burns) and

BLEVE Scenario (Fireball + Fatal Burns).

The second most important task is to implement an input validation system.

This system helps to prevent the user from entering invalid inputs for

calculations. The system work by returning a message window detailing which

input/s is invalids.

Online help documents for each of the detailed analysis models is an essential

addition to the current HEVAN package. So far only two models from the

current library has this feature. The documentation should contain details

regarding the general usage of the models and detailed explanation of how the

models work.

Another great improvement is to allow the users to export the output data from

hevancal to a spreadsheet program such Microsoft Excel. In this way, the users

will be able to interpolate the data with more precise methods and also able to

generate custom plots for presentation.

Other useful features such as the ability to customise the plots online can be a

good addition to the HEVAN package. The users may be able to set the scales

of the axes, show a grid, edit the title and axes, and select the colours used for

the plot.


31/56

-

8.0 CONCLUSION

There has been positive efforts made toward the completion of the Individual

Inquiry objectives, however, there are still a lot of work to be done to continue

the development of the HEVAN package. Five new models had been added tothe current collection of detailed analysis models. The material property

database had been upgraded to handle up to 36 components. The overall

structure of the Web site had been revised and restructures to make it more user-

friendly. There are still a lot of work to be completed to develop HEVAN to a

stage where it could be used for the purpose it designed for.


32/56

-

9.0 REFERENCES

[1] HAZMAT

http://hazmat.dot.gov/risk-def.htm

[2] Cameron, I. (1996) Safety Engineering: Planning for Safe Design,

Control and Operation of Process Systems, Department of Chemical

Engineering, UQ, Brisbane.

[3] Wong, B. (1999) Interactive Risk Management Web Tool,

Undergraduate Thesis, UQ, Brisbane.

[4] He, J. (1998)Internet Resources for Engineers, Reed International, Port

Melbourne.

[5] Castro, E. (1996) HTML for the World Wide Web, Peachpit Press,

Berkeley.

[6] Zhang, T. (1997) Teach Yourself C in 24 hours, Sam Publishing,

Indianapolis.

[7] TNO (1992)Methods for the Calculation of Physical Effect, 2nd

edition,

TNO, Voorburg.

[8] TNO (1997)Methods for the Calculation of Physical Effect, 3rd

edition,

TNO, Voorburg.


33/56

-

APPENDIX 1

MODELS TO BE IMPLEMENTED


34/56

-

The models to be added to the current collection are:

Liquid Outflow from a Pipe Liquefied Outflow from a Pipe BLEVE Scenario (Fireball + Second Degree Burns) BLEVE Scenario (Fireball + Fatal Burns)

The source code (CPP) files for the two outflow models have been pre-written.The models only need to be revised/debugged before it can be implemented.


35/56

-

APPENDIX 2

LISTS OF FILES IN HEVAN SUB-DIRECTORIES


36/56

-

Table A2-1 docs directory listing

File Name DescriptionAdgcode.htm Australian dangerous goods classificationBleve.htm BLEVE

Contdisp.htm Continuous pt dispersion

Detaildb.htm Current substance DBDgclassif.html Dangerous goods classification

Effectmain.htmlMain pageEffects.htm Effects advice

Gaspipe.html Gas release from a pipeGasvessel.html No permissionLiqvessel.html No permissionOlddocs.htm Hevan online docRisk.phrases.htm Risk phrases

Safetyphrases.htm Safety phrasesSegregate.html Substance incompatibility

Substances.htm Substance advice

Table A2-2 indexes directory listing

File Name DescriptionDetailed DAM menu

Dispers Dispersion models

Explosion Explosion modelsFire Fire modelsOverview Old menu (?)

Release Release modelsShortcut Shortcut menu

Table A2-3 shortcuts directory listing

File Name Description

Bleve_impact Liquefied flammable gas BLEVEEnclosuretable Substance scenario tableExplosion_impact Explosion impacts (TNT equivalent model)

Fireflash Flammable liquid flash fireFirepoolsp33 Pool fire impacts based on total quantity (sepp33)Firepooltno Pool fire impacts based on pool area

Liqflamgascont Liquefied flammable gas continuous release and flash fireLiqflamgasinst Liquefied flammable gas instant release and flash fireLiqrelease liquid release rates for pressurised gas

Pressgas Pressurised flammable gas flash fire fatality impactPressgasjet Pressurised flammable gas jet fire fatality impactPressgassp33 Pressurised flammable gas flash fire (sepp33)

Shortcut No permissionTablet234 Toxic substances (class 6) impact ratingsToxcompliqgasfat Toxic cloud compressed liquefied gas fatal impacts

Toxcompliqgasinj Toxic cloud compressed liquefied gas injury impactsToxcoolgasfat Toxic cloud - cooled liquefied gas fatal impactsToxcoolgasinj Toxic cloud cooled liquefied gas injury impacts

Toxevapliqfat Evaporating toxic liquid fatal impactsToxevapliqinj Evaporating toxic liquid injury impactsToxpowf Toxic cloud powders fatal impacts

Toxpoxi Toxic cloud powders injury impacts


37/56

-

Toxpressgasfat Toxic cloud pressurised gas fatal impactsToxpressgasinj Toxic cloud pressurised gas injury impacts

Vaprelease Vapour release rates for pressurised gas


38/56

-

APPENDIX 3

SAMPLE TEMPLATE FILES OF HEVAN MODEL


39/56

-

Sample HTML template page

Thermal Radiation from a Pool Fire

This calculation estimates the heat flux from a rectangular pool fire at an

object.


40/56

-

ENVIRONMENTAL DETAILS:

Relative Humidity (%)

Ambient Temperature (deg C)

Wind Speed (m/s)

Emittance of Clear Flame (kW/m2)

Emittance of Smokey Flame (kW/m2)

(code = c6s3223)

Sample input (inp) template page

[Calculation]

Event = Radiation

Title = Thermal Radiation from a Pool FireY-Label = Heat Flux (kW/m2)X-Label = Distance between Object and Edge of Pool (m)

Output = GNUPLOT

[Event]ID = Radiation

TYPE = PoolFireRadiation; Length of Pool (m)

Parameter 1 = {length}


41/56

-

; Width of Pool (m)

Parameter 2 = {width}; Mass Burning Rate (kg/m2.s)

Parameter 3 = {rate}; Carbon to Hydrogen ratio of Fuel

Parameter 4 = {ratio}; Distance between Object and Edge of Pool (m)

Parameter 5 = {distance}; Wind Speed (m/s)

Parameter 6 = {wind}; Relative Humidity (%)

Parameter 7 = {humidity}; Ambient Temperature (deg C)

Parameter 8 = {temperature}; Emittance of Clear Flame (kW/m2)

Parameter 9 = {clear}; Emittance of Smokey Flame (kW/m2)

Parameter 10 = {smokey}

; Height to Tank Top (m)Parameter 11 = {height}; Material Code

Parameter 12 = {material}


42/56

-

APPENDIX 4

SOURCE CODES OF THE MODELS IMPLEMENTED


43/56

-

The following are the source codes of the models implemented at the

completion of this Individual Inquiry. The source codes for the main calculationprograms in HEVAN directories can be access from [3].

Thermal Radiation from a pool fire (c6s3223.cpp)

/*

** Calculation of Radiation from a Rectangular Pool Fire

** using a View Factor (Surface Source) method.

**

** Chapter 6, section 3.2.2.3**

** TNO Report CPR 14E, Methods for the calculation of

** physical effects, 2nd Edition, Voorburg, 1992.

**

** and**

** Pritchard, M.J. and T.M. Binding, FIRE2: A New Approach

for Predicting

** Thermal Radiation Levels from Hydrocarbon Pool Fires,

IChemE Sym Ser

** 130, 491-505, 1992

**

** Craig Newell, December 1992

** Ian Cameron, November 1993 (revision 1).

** Alfred Aukes, December 1993 (revision 2) Flame Tilt

** Ian Cameron, November 1994 (revision 3) change input units

to degrees C

** Ian Cameron, October 2000 (revision 4) Tilted cylinder view factor added*/

#include hevancal.h

double heat_rad_rect_pool_fire_vf ( double *incid_par){

double l, w, h_f, d_p, d_eq, Ft, Fc, Fs, u, Lf, Lcf, Ecf, Esf,

Ecomp, x, mdotdot, rho_a, Tau_a, percent_RH, C_H_ratio, m_star,U9_star, Uc, E, mat_code, load, load_cf, load_sf,

T_a, mdotdot2, Fr, Re, theta_old ,K , a, b, c, fa, fb, fc,load_t, u_star, theta, rho_v, t_bp, mol_wt, ttop, thetarads,

L1, L2, Ft1, Ft2, x1, load_comp, load_comp_ttop, Fall1, Fall2,

Fw;int max_it, m_code;


44/56

-

l = incid_par[0] ; /* length of pool (m) -

always the longest side */

w = incid_par[1] ; /* width of pool (m) */

mdotdot = incid_par[2] ; /* mass burning rate

(kg/m2.s) */

C_H_ratio = incid_par[3] ; /* carbon to hydrogen ratio

of fuel */

x = incid_par[4] ; /* distance between object

and flame (m) */

u = incid_par[5] ; /* windspeed (m/s) */

percent_RH = incid_par[6] ; /* percent relative humidity

(%) */

T_a = incid_par[7] ; /* atmospheric temperature */

Ecf = incid_par[8] ; /* emittance of clear flame

(kW/m2) */

Esf = incid_par[9] ; /* emittance of smokey flame

(kW/m2) */

ttop = incid_par[10] ; /* height to tank top (m) */

m_code=incid_par[11]; /* material code */

/* Convert to true SI units */

T_a = T_a + 273.15 ;if ( ( l / w ) == 1 ) {

d_p = ( l + w ) / 2 ;} else if ( ( l / w ) < 2 ) {

d_eq = ( 4 * l * w ) / ( 2 * ( l + w ) ) ;/* equation 19 */

d_p = d_eq ;

} else if ( (l / w ) > 2 ) {d_eq = ( 4 * ( 1.5 * w ) * w ) / ( 2 * ( ( 1.5 * w ) + w ) ) ;

/* equation 19 modifiedas in text just below */

d_p = d_eq ;

}

printf(\n\n\n Equivalent Diameter of fire = %g (m), d_p ) ;printf(\n Area of fire = %g (m2), l*w ) ;

rho_a = 1.2 ; /* density of air (kg/m3) */ /* Calculate the mass burning rate (kg/m2.s) Zabetakis & Burgess (1961) */

mdotdot2 = 0.141 * (1 - exp(-0.136 * d_p)) ;printf(\n Calculated mass burning rate (SHELL) = %g (kg/m2.s), mdotdot2) ;

/* Calculate the flame height (m) using the Thomas formula */h_f = d_p * 42 * pow( ( mdotdot / ( rho_a * sqrt ( GRAVITY * d_p ) ) ),


45/56

-

0.61 ) ;

printf(\n Flame height at specified burn rate (Thomas method) = %g (m), h_f);

/* equation 4 *//* Calculate the flame height (m) using British Gas method (1992) */

m_star = mdotdot / (rho_a * sqrt( GRAVITY * d_p)) ;Uc = pow ( (GRAVITY * mdotdot * d_p / rho_a), 0.333 ) ;

U9_star = u / Uc ;if ( U9_star < 1 ) {

U9_star = 1 ;

}

Lf = 10.615 * pow( m_star, 0.305 ) * pow( U9_star, -0.03) * d_p ;

printf(\n\n British Gas approach gives:) ;printf(\n Total flame height = %g (m), Lf );

Lcf = 11.404 * pow( m_star, 1.13 ) * pow( U9_star, 0.179 ) *pow( C_H_ratio, -2.49 ) * d_p ;

printf(\n Clear flame length = %g (m), Lcf ) ;/* Calculate the flame tilt due to wind effects using British Gas data */

if ( u > 0 ) {Re = d_p * u / 1.5e-5 ;

Fr = u * u / GRAVITY / d_p ;/* Iterate for solution of tilt equation */

K = pow(Fr,0.333)*pow(Re,0.117)*2./3.;theta_old = 0.9 ;

max_it = 1 ;a = 0.1 ;

b = PI / 2 ;while (fabs(tan(theta_old) -

cos(theta_old)*pow(Fr,0.333)*pow(Re,0.117)*2./3.) > 1e-3 ) {max_it = max_it +1;

fa = tan(a)/cos(a)-K ;fb = tan(b)/cos(b)-K ;

c = (a + b) / 2 ;fc = tan/cos-K ;

if (fa * fc < 0) b = c;else if (fb * fc < 0) a = c;

theta_old = c;if (max_it >= 50) break;}

theta_old = theta_old * 180 / PI;}

else{

theta_old = 0.0 ;}

printf(\n Windspeed is %g m/s , u) ;

printf(\n The flame tilt is %g degrees for British Gas.,(theta_old));/* Calculate flame tilt using Thomas/AGA method */


46/56

-

if (u


47/56

-

Fc = view_factor_tiltcylindrical( x+d_p/2, Lcf, d_p/2, theta ) ;

Fs = view_factor_tiltcylindrical( x+d_p/2,(Lf - Lcf), d_p/2, theta ) ;}

else{

Ft = view_factor_flat( x, Lf, l ) ;Fc = view_factor_flat( x, Lcf, l ) ;

Fs = view_factor_flat( x, (Lf - Lcf), l ) ;}

printf(\n\n View Factors:) ;printf(\n clear flame = %g, Fc) ;

printf(\n smokey flame = %g, Fs) ;

printf(\n total flame = %g, Ft) ;

Tau_a = find_Tau_a( x, percent_RH, T_a ) ;

printf( \n Transmissivity = %g, Tau_a ) ;/* E = find_E( mat_code, T_a, eta, (l + w) / 4 ) ; */

printf( \n\n Emittance of clear flame = %g (kW/m2), Ecf ) ;

printf( \n Emittance of smokey flame = %g (kW/m2), Esf ) ;printf( \n Emittance of composite flame = %g (kW/m2), 0.8*Esf+0.2*Ecf) ;

load_cf = Ecf * Fc * Tau_a ;load_sf = Esf * Fs * Tau_a ;

load = load_cf + load_sf ;load_t = Ecf * Ft * Tau_a ;

load_comp = (Ecf*0.2 + Esf*0.8)*Ft*Tau_a ;

if( ttop > 0 ) {load_comp_ttop = Ecomp * Ft * Tau_a ;

printf(\n Load from tank top flame (at composite emittance) = %g (kW/m2),load_comp) ;

}

printf(\n\n Load from clear flame = %g (kW/m2), load_cf) ;printf(\n Load from smokey flame = %g (kW/m2), load_sf) ;

printf(\n Load from combined flame = %g (kW/m2), load) ;printf(\n Load from total flame (at clear flame emittance) = %g (kW/m2),

load_t) ;printf(\n Load from total flame (at composite emittance) = %g (kW/m2),

load_comp) ;/* equation 7 */

return( load_comp ) ;

}


48/56

-

Dispersion of Gas from a continuous area source (c7s382.cpp)

/*

**

** Concentration due to a continuous area of point sources

** Chapter 7. Section 3.8.

**

** Craig Newell January, 1993.

** Ian Cameron March 1993 (revision 1)

** Kien Tran October 2000

**

*/

#include hevancal.h

double dispersion_cont_area(double *incid_par)

{

double z_o, h, u_w, C, m_dot, t_dash, delta_x,

x_dash, L_x,

L_y, L_z , x, y, z;

int stability, N, i ;

z_o = incid_par[0] ; /* roughness factor (m) */

stability = incid_par[1] ; /* number 1 to 6 (A-F) */

u_w = incid_par[2] ; /* wind at 10m (m/s) */

t_dash = incid_par[3] ; /* averaging time (min) */

m_dot = incid_par[4] ; /* outflow rate (kg/s) */

h = incid_par[5] ; /* height of source (m) */

L_z = incid_par[6] ; /* height of plume (m) */

L_x = incid_par[7] ; /* width of plume (m) */

L_y = incid_par[8] ; /* length of plume (m) */

x = incid_par[9] ; /* x coordinate */

y = incid_par[10]; /* y coordinate */

z = incid_par[11]; /* z coordinate */

N = incid_par[12]; /* no. of summations */

C = 0 ;


49/56

-

if ( L_x == 0 ) {

C = ( m_dot / u_w ) * F_y( x, y, L_y , t_dash, stability, h ) *F_z( x, z, L_z , h, z_o, stability ) * 1e6 ;

} else if ( L_x > 0 ) {

if ( L_x >= fabs(x) && fabs(y)


50/56

-

}

double F_y( double x, double y, double L_y, double t_dash, double stability,double h ){

double sigma_y, F ;

sigma_y = set_sigma_y( x, t_dash, stability, h ) ;

/*

printf(\n sigma_y = %f , sigma_y ) ;*/

F = 0 ;if ( L_y == 0 ) {

F = ( 1 / ( 2.506628275 * sigma_y ) ) *

exp( -1 * ( y * y ) / ( 2 * ( sigma_y * sigma_y ) ) ) ;

/* equation 11c */

} else if ( L_y > 0 ) {

F = ( 0.25 / L_y ) * (

erf( ( L_y - y ) / ( sigma_y * 1.414213562 ) ) +

erf( ( L_y + y ) / ( sigma_y * 1.414213562 ) ) ) ;

/* equation 11d */

}

return (F) ;

}

double F_z( double x, double z, double L_z, double h, double z_o,

double stability )

{

double F, sigma_z ;

sigma_z = set_sigma_z( x, z_o, stability, h ) ;

/*


51/56

-

printf(\n sigma_z = %f , sigma_z ) ;*/

F = 0 ;

if ( L_z == 0 ) {

F = ( 1 / ( 2.506628275 * sigma_z ) ) * (

exp( -1 * ( z - h ) * ( z - h ) / ( 2 * ( sigma_z * sigma_z ) ) ) +exp( -1 * ( z + h ) * ( z + h ) / ( 2 * ( sigma_z * sigma_z ) ) ) ) ;

/* equation 11e */

} else if ( L_z > 0 ) {

F = ( 0.25 / L_z ) * (

erf( ( L_z - z + h ) / ( sigma_z * 1.414213562 ) ) +

erf( ( L_z + z - h ) / ( sigma_z * 1.414213562 ) ) +erf( ( L_z - z - h ) / ( sigma_z * 1.414213562 ) ) +

erf( ( L_z + z + h ) / ( sigma_z * 1.414213562 ) )) ;

}

return (F) ;

}

Continuous point source dispersion contours (c7s39.cpp)

/*

**

** Concentration contour due to a continous point source

** Chapter 7. Section 3.9.

**

** TNO Methods for the Calculation of Physical

** Effects, CPR14E, Voorburg, 1992 (2nd Edn).

**

**

** Alfred Aukes December 1993

** Kien Tran October 2000

**

*/


52/56

-

#include hevancal.h

double plume_contour ( double *incid_par)

{

double C, x_vy ,L_y ,a ,b ,c ,d ,C_t ,x_hat

,sigma_y ,sigma_z,

z_o, stability, u_w, t_dash, m_dot, h, L_z,

x_vz,

yt, Ccont, x, y, z;

z_o = incid_par[0] ; /* roughness factor (m) */

stability = incid_par[1] ; /* number 1 to 6 */

u_w = incid_par[2] ; /* wind at 10m (m/s) */

t_dash = incid_par[3] ; /* conc. averaging

time (min) */

m_dot = incid_par[4] ; /* outflow rate (kg/s) */

h = incid_par[5] ; /* height of source (m) */

L_z = incid_par[6] ; /* height of source */

L_y = incid_par[7] ; /* width of source */

x = incid_par[8] ; /* x coordinate */

y = incid_par[9] ; /* y coordinate */

z = incid_par[10] ; /* z coordinate */

Ccont = incid_par[11] ; /* concentration of interest

(mg/m3) */

C_t = pow((t_dash/10),0.2) ;

C = set_stability(stability,h,&a,&b,&c,&d) ;

if (z_o!=0.1) {

c = c * 1.98 * log(10 * z_o);

d = d - 0.059 * log(10 * z_o);}

x_vy = pow((L_y / (2.15 * a * C_t)),(1/b));

x_vz = pow((L_z / (2.15 * c)),(1/d));

// x_hat = pow((m_dot / (PI * u_w * a * C_t * c * Ccont)),(1/(b+d))) -x_vy ;

//printf(y = %5.5f\n,x_hat);/* Equation 14a */


53/56

-

sigma_z = set_sigma_z( x + x_vz , z_o , stability,h) ;

sigma_y = set_sigma_y( x + x_vy ,t_dash,stability,h) ;

printf( Vertical coeff = %g (m), Horiz coeff = %g (m)\n,sigma_z,sigma_y);

C = ( m_dot / ( 2 * PI * u_w * sigma_y * sigma_z ) ) *

exp( -1 * ( y * y ) / ( 2 * sigma_y * sigma_y ) ) *

( exp( -1 * ( z - h ) * ( z - h ) / (2 * sigma_z * sigma_z )) +exp( -1 * ( z + h ) * ( z + h ) / (2 * sigma_z * sigma_z )) ) ;

/* equation 11 */ C = C * 1e6;

if (C


54/56

-

stability = incid_par[7]; /* Pasquill Stability Factor

*/

/* dispersion coefficients */if (stability == 1) {

sigma_x = 0.18*pow(x,0.92);

sigma_z = 0.60*pow(x,0.75);

}

if (stability == 2) {

sigma_x = 0.14*pow(x,0.92);

sigma_z = 0.53*pow(x,0.73);

}


sigma_x = 0.10*pow(x,0.92);

sigma_z = 0.34*pow(x,0.71);

}


sigma_x = 0.06*pow(x,0.92);

sigma_z = 0.15*pow(x,0.70);

}


sigma_x = 0.04*pow(x,0.92);

sigma_z = 0.10*pow(x,0.65);

}


sigma_x = 0.02*pow(x,0.92);

sigma_z = 0.05*pow(x,0.61);

}

sigma_y = sigma_x;printf(\nsigma x = %g, sigma_x);printf(\nsigma y = %g, sigma_y);

printf(\nsigma z = %g, sigma_z);

/* main equation - concentration */

C = Q/(pow(6.283185307, 1.5)*sigma_x*sigma_y*sigma_z)*

exp(-0.5*pow((y/sigma_y),2))*exp(-0.5*pow((x-u*t)/sigma_x,2))*(exp(-0.5*pow((z-H)/sigma_z,2))+exp(-0.5*pow((z+H)/sigma_z,2)));


55/56

-

C = C*1000000; /* convert to mg/m^3 */

printf(\nThe time is %g., t);

printf(\nThe concentration is %g mg/m^3., C);

return( C );}

Vapour Cloud Explosion (TNT Equivalent) (tntequiv.cpp)

/*

**

** VCE Model (TNT Equivalence)

** Benajmin Wong (2000)

**

*/

#include hevancal.hdouble tntequiv (double *incid_par) {

double Q_tnt, r2, P, Q_f, alpha, E_mf, E_mTNT, r;

Q_f = incid_par[0];

E_mf = incid_par[1];alpha = incid_par[2];

r = incid_par[3];

E_mTNT = 5420;

Q_tnt = alpha*(Q_f*E_mf)/E_mTNT;

r2 = r/pow(Q_tnt,0.333);

P = 694.46*pow(r2,-1.5542);

return(P);

}


56/56

-

GLOSSARY

This is a glossary of the terms used in this report that may be unfamiliar to the

readers.

CGI

Common Gateway Interface, a method of allowing programs on a Web server to

be run using data sent from a Web browser.

HTML

Hypertext Markup Language, the code used to create Web pages.

make

Method of compiling a large program made up of many files or folders.

makefile

A file which determine how to make a program.

UNIX

Type of operating system. Common operating system used for Web server.

Documents

interactive web based risk assessment system.pdf