Manual flacs

FLACS v9.0 User’s Manual
Copyright ©GexCon AS
Thursday March 12 2009

Contents
1 Introduction 1
1.1 About this publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 About this manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Feedback from users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Getting started 7
2.1 Prerequisites for users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Hardware and software requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Software installation and setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Running FLACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5 Help and support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.6 Introductory example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3 CASD 31
3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2 File menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3 Geometry menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4 Object window in CASD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.5 Grid menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.6 Porosities menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.7 Scenario menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.8 Block menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
3.9 View menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
3.10 Options menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
3.11 Macro menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.12 Help menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
3.13 Potential bugs or problems with CASD . . . . . . . . . . . . . . . . . . . . . . . . . 110

ii CONTENTS
4 Flacs simulator 113
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
4.2 The Run Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
4.3 Running several simulations in series . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.4 Output variables in FLACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
4.5 Files in FLACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
4.6 Input files to FLACS simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
4.7 Output files from FLACS simulations . . . . . . . . . . . . . . . . . . . . . . . . . . 149
4.8 Potential bugs or problems with Flacs . . . . . . . . . . . . . . . . . . . . . . . . . . 153
4.9 Warning and error messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
5 Flowvis 155
5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
5.2 Creating a new presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
5.3 File menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
5.4 Edit menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
5.5 Page menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
5.6 Plot menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
5.7 Verify menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
5.8 Options menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
5.9 Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
5.10 Flowvis examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
6 Utility programs in FLACS 187
6.1 Geometry, grid and porosities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
6.2 Release source modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
6.3 Modifying simulation files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
6.4 Post-processing of simulation data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
7 Best practice examples 205
7.1 Combined dispersion and explosion simulations with FLACS . . . . . . . . . . . . 206
7.2 Simulation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
7.3 Equivalent Stoichiometric Gas Cloud . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
7.4 Dispersion simulation with wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
7.5 Hydrogen explosions and DDT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
8 Technical Reference 221
8.1 Definitions and gas thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

CONTENTS iii
8.2 Stoichiometric reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
8.3 Governing equations for fluid flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.4 Wall functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
8.5 Wind boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
8.6 Combustion modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
8.7 Modelling of jet sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
8.8 Numerical Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
8.9 Linux Quick Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
9 Nomenclature 237
9.1 Roman letters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
9.2 Greek letters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
9.3 Subscripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
9.4 Dimensionless groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
9.5 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
9.6 FLACS variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
10 References 243

Chapter 1
Introduction
1.1 About this publication
Copyright ©2009 GexCon AS
All rights reserved
Updated: January 26 2009
Typeset in Doxygen
Printed in Norway
Intellectual property notice
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in
any form or by any means, electronic, mechanical, photocopying, or otherwise, without written
permission from GexCon AS.
GexCon AS hereby grants permission to use, copy, and print this publication to organizations or
individuals holding a valid licence for one or several of the software packages described herein.
For further information about GexCon AS, please visit the web site: http://www.gexcon.com
Exclusion of liability
GexCon AS has distributed this publication in the hope that it will be useful, but without any
warranty, without even the implied warranty of merchantability or fitness for a particular pur-
pose.
Although great care has been taken in the production of this publication to ensure accuracy,
GexCon AS cannot under any circumstances accept responsibility for errors, omissions, or advice
given herein.

2 Introduction
Registered trademarks
• FLACS, DESC, CASD, and Flowvis are registered trademarks of GexCon AS.
• Linux is a registered trademark of Linus Torvalds.
• Windows is a registered trademark of Microsoft Corporation.
Other product names mentioned herein are used for identification purposes only and may be
trademarks of their respective companies.
1.2 Preface
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical methods
and algorithms to solve and analyze problems that involve fluid flow, with or without chemical
reactions. Current use of CFD covers a broad range of applications, from fundamental theoret-
ical studies involving models primarily derived from first principles, to practical engineering
calculations utilizing phenomenological or empirical correlations.
Many of the hazards encountered in the society, and especially in the process industries, involve
accident scenarios where fluid flow in complex, large-scale, three-dimensional (3D) geometries
play a key role. FLACS is a specialized CFD toolbox developed especially to address process
safety applications such as:
• Dispersion of flammable or toxic gas
• Gas and dust explosions
• Propagation of blast and shock waves
• Pool and jet fires
The development of FLACS started in 1980 at the Department of Science and Technology at Chris-
tian Michelsen Institute (CMI). CMI established GexCon (Global Explosion Consultants) as a con-
sultancy activity under the Process Safety Group in 1987. In 1992, the Science and Technology
department at CMI became Christian Michelsen Research (CMR), and CMR established GexCon
as a private limited company in 1998. GexCon AS is a wholly owned subsidiary of CMR, and
holds the full proprietary rights to the CFD code FLACS.
The purpose of this manual is primarily to assist FLACS users in their practical work with the
software. In addition, the manual aims at documenting both the physical and chemical models,
and the numerical schemes and solvers, implemented in the CFD code. Ample references to
published literature describe the capabilities and inherent limitations of the software.
1.3 Acknowledgements
The development of the FLACS software would not have been possible without the generous
contributions received from supporting companies and government institutions throughout the
years. The activity started at Christian Michelsen Institute (CMI) in 1980 with the Gas Explosion
Programmes (GEPs), and FLACS-86 was the first version distributed to the supporting compa-
nies.

1.3 Acknowledgements 3
Figure 1.1: The M24 compressor module represented in FLACS-86
The development of FLACS continued with the Gas Safety Programs (GSPs) and related projects
up to around 2000:
• BP, Elf, Esso (Exxon), Mobil, Norsk Hydro, and Statoil supported the development of
FLACS-86 during the First GEP (1980-1986).
• BP, Mobil, and Statoil supported the development of FLACS-89 during the Second GEP
(1986-1989).
• BP, Elf, Esso, Mobil, Norsk Hydro, Statoil, Conoco, Philips Petroleum, Gaz de France, NV
Nederlandse Gasunie, Bundes Ministerium für Forschung und Technologie (BMFT), Health
and Safety Executive (HSE), and the Norwegian Petroleum Directorate supported the de-
velopment of FLACS-93 during the First GSP (1990-1992).
• BP, Elf, Esso, Mobil, Statoil, Philips Petroleum, Gaz de France, HSE, and the Norwegian
Petroleum Directorate supported the development of FLACS-94, FLACS-95, and FLACS-96
during the Second GSP (1993-1996).
• BP, Elf, Exxon, Mobil, Norsk Hydro, Statoil, Philips Petroleum, Gaz de France, HSE,
Agip, MEPTEC, and the Norwegian Petroleum Directorate supported the development of
FLACS-97, FLACS-98, and FLACS-99 during the Third GSP (1997-1999).
• BP, TotalElfFina (TEF), Norsk Hydro, Statoil, Gaz de France, Philips Petroleum, Mobil and
supported the LICOREFLA project (2000-2001).
Since 2000, various Joint Industry Projects (JIPs), funding from the European Commission (EU)
and the Norwegian Research Council (NFR), and support and maintenance fees (S&M) from an
increasing number of commercial costumers have supported the development of the more recent
FLACS releases, including several specialized versions of FLACS, such as DESC (Dust Explosion
Simulation Code), FLACS-Dispersion, and FLACS-Hydrogen:
• FLACS-Dispersion and FLACS-Hydrogen became available in 2001.
• FLACS v8.0 came in 2003, including a test release of FLACS-Explo.
• FLACS v8.1 came in 2005.

4 Introduction
• DESC 1.0 came in 2006.
• FLACS v9.0 came in 2008, including a test release of FLACS-Fire.
• GexCon also develops several in-house R&D tools, including FLACS-Explo, FLACS-
Aerosol, and FLACS-Energy.
GexCon is grateful to all companies, government institutions, and individuals that have partici-
pated in the development of FLACS. We intend to honour these contributions by continuing to
develop the software, and thereby contribute to improved safety in the process industries.
1.4 About this manual
This User’s Manual describes a family of computational fluid dynamics (CFD) software products
from GexCon AS, generally referred to as FLACS:
• The preprocessor CASD
• The CFD simulator Flacs
• The postprocessor Flowvis
• Utility programs in FLACS such as:
– geo2flacs, gm, and Porcalc
– jet and flash
– rdfile, cofile, and comerge
– r1file, r3file, and a1file
These programs constitute a specialized CFD tool, FLACS, or ’standard FLACS’, designed to
study releases of flammable gas and gas explosions in complex congested geometries, both on-
shore and offshore. This manual also describes specialized versions of FLACS:
• FLACS-Hydrogen
• FLACS-Dispersion
• FLACS-Aerosol
• FLACS-Energy
• FLACS-Explo
• FLACS-Fire
• DESC
A full version of Standard FLACS exhibits the full functionality of FLACS-Hydrogen and FLACS-
Dispersion, whereas DESC and FLACS-Fire are separate software products. FLACS-Energy,
FLACS-Explo, and FLACS-Aerosol are still in-house R&D tools. The acronym FLACS (FLame
ACceleration Simulator) refers to the complete package of software products, whereas the term
Flacs refers specifically to the numerical solver in the CFD code.
The latest release of FLACS is version 9.0 (FLACS v9.0). This version represents a major upgrade
to the graphical user interfaces (GUIs), and is the first version that runs under both the Linux and
Windows operating systems.
Getting started presents a detailed example for new users of FLACS, and Best practice examples
contains further examples that highlight various applications of FLACS, including some of the
specialized versions.
Technical reference contains technical reference material.

1.4 About this manual 5
1.4.1 Printing conventions in this manual
• The symbol ’>’ followed by text in typewriter font indicates command line input, e.g.:
> command -options arguments (general syntax for commands)
> find -name flacs (command line input in Linux)
• The symbol ’∗’ followed by text in typewriter font field input commands, e.g.:
∗ exit yes yes
• The symbol→indicates a path through nested menu items or dialog box options, e.g.:
File→Save
Scenario→Ignition→Time of ignition
• Certain features of the software may only be accessible through text file input, and the
content of a text file is also printed in typewriter font:
THE FIRST LINE OF THE FILE ...
THE SECOND LINE OF THE FILE ...
... ...
• The format for describing keyboard and mouse input follows the pattern:
CTRL+C
CTRL+MOUSE+LEFT
• The use of bold or italic font emphasizes specific words or phrases in the text.
• The Nomenclature chapter lists the symbols and abbreviations adopted in this manual.
1.4.2 Special messages
Warning:
Look out for the potential pitfalls pointed out by this heading!
Attention:
Be aware of practical information pointed out by this heading.
Remarks:
Take notice of the points summarized under this heading.
See also:
Follow up the additional sources of information suggested by this heading if required.
1.4.3 Job numbers
The typical application of the FLACS software is to quantify potential consequences of industrial
accident scenarios involving compressible fluid flow, with or without chemical reactions. Proper
characterization of a particular problem may involve several simulations, and it is usually conve-
nient to organize the files from related scenarios in a dedicated directory. The individual FLACS
simulations are assigned job numbers, or simulation numbers, or simply jobs. A user may for
instance type:
> run9 flacs 010100
on the command line in Linux to start a FLACS simulation for job number 010100.
The job numbers are constructed from a six-digit string ijklmn, where traditionally:

6 Introduction
• ij is the project number.
• kl is the geometry number.
• mn is the sequence number.
The default job number used in many of the examples in this manual is 010100, i.e. project 01,
geometry 01, simulation 00. However, each of the six digits in the job number may in principle
take on any integer value from zero to nine, and the references to project, geometry, and sequence
numbers only apply when the job numbers are derived from the file database in CASD.
Any updated version of this manual may be found on the FLUG web site.
1.5 Feedback from users
Feedback on the content in this manual is most welcome, and FLACS users may submit their
comments or suggestions by e-mail to: flacs@gexcon.com
When submitting comments or suggestion to the content of the manual, or when pointing out
misprints in the text, please indicate the relevant page numbers or sections, and the correspond-
ing version of the manual (date issued).

8 Getting started
This chapter describes the basics of setting up the FLACS software for new users, including rec-
ommendations concerning the user threshold, typical hardware requirements, and procedures
for installing FLACS on both Linux and Windows.
2.1 Prerequisites for users
Efficient use of FLACS does not require detailed knowledge about computational fluid dynam-
ics (CFD). However, users should possess some experience in the application of computers for
routine tasks, such as text editing. Proper interpretation of simulation results requires adequate
knowledge within the field of fluid dynamics. A suitable starting point for the novice in the field
of gas explosions is the Gas Explosion Handbook (Bjerketvedt et al., 1993) from Christian Michelsen
Research (CMR), and new users of FLACS should attend a three-day introductory course arranged
by GexCon AS (http://www.gexcon.com).
2.2 Hardware and software requirements
FLACS v9 is available on Linux and on Microsoft Windows. The hardware requirements for
running the FLACS software depend to some extent on the size of the problem in question, i.e.
the number of grid cells required to resolve the computational domain properly. Most modern
computers, be it desktops and laptops, will perform well for small or medium sized problems.
A powerful screen card may be required to handle large geometries in CASD, extra memory
(RAM) is necessary for simulating large problems, and storage of large amounts of simulation
data dictates the requirements for disk space.
Hardware requirements:
• Processor: Intel or AMD ix86 32 bit, Intel EM64T or AMD64. Intel IA64 is not supported.
• Internal memory; 2GB or more recommended.
• Free harddrive capacity: 350MB for software installation and typically 100GB simulation
space.
• Graphics card using NVIDIA chip set. Graphics cards using for instance ATI or Intel
chipsets are in general not supported.
• DVD-RW drive recommended.
• High resolution colour screen (minimum 19", 1600x1200, 24 bit color depth).
FLACS v9 has been tested on the following platforms.
Linux:
• OpenSuse 10.0, 10.2, 10.3, 11.0
• CentOS 4.6, 5.1
• Ubuntu 7.10
• Fedora 8
Microsoft Windows:
• XP (32 bit)
• Vista (32 bit)

2.3 Software installation and setup 9
Red Hat Enterprise Linux 4.6, 5.1 is expected to be FLACS v9 compatible since it is compatible
with CentOS 4.6, 5.1.
For updated hardware and software requirements, please refer to GexCon’s website,
http://www.gexcon.com .
2.3 Software installation and setup
A license server is necessary for running FLACS. This section presents FLACS installation, the
FLACS Licence Server and the FLACS Configuration Wizard that guides users through the basic
steps of setting up a FLACS Licence Server. All FLACS installations on a network acquire their
individual licenses from a central licence server, and only one FLACS License Server should
therefore be running on a given network.
FLACS is distributed in a single setup file.
2.3.1 On Linux
On Linux FLACS can be installed system wide, in which case FLACS will be available to all users,
or in a user’s home directory, in which case it will be available to this user only.
2.3.1.1 Installing in users home directory
If only one person will be using FLACS, the software can be installed in this users home directory.
FLACS will by default be installed under /home/my_user/GexCon.
Save the installation package to a convenient location.
Make sure the file is executable:
> chmod u+x /home/my_user/flacs-v9.0-installer
Run the installation program:
> /home/my_user/flacs-v9.0-installer
Please follow the instructions given. It is recommended to keep the default parameters.
FLACS requires a license to run. The license is provided by a license server, which is installed on
only one machine on the local network. During the installation the user can choose to install:
1. Both FLACS software and FLACS license manager
2. FLACS license manager only
For a user home directory installation option 1 should be selected.
The FLACS license manager must be set up before using FLACS. Please refer to the section about
FLACS configure wizard.
2.3.1.2 Installing system wide as super user
To install FLACS system wide, access to the system super user ("root") is required.
/path/to/installation is the path to the location of the FLACS installation package.

10 Getting started
Change user to super user ("root"):
> su <give password>
Make sure the file is executable:
> chmod u+x /path/to/installation/flacs-v9.0-installer
Run the installation program:
> /path/to/installation/flacs-v9.0-installer
Please follow the instructions given. It is recommended to keep the default parameters.
Option 2 can be used to install a FLACS license manager on a system not running FLACS. Alter-
natively one FLACS workstation in the network can be set up to serve licenses to all other FLACS
installations in the network.
The FLACS license manager must be set up before using FLACS. Please refer to the section about
FLACS configure wizard.
2.3.2 On Windows
To install FLACS on Windows please double-click the installation package "flacs-v9.0-
installer.exe". This will start the installation wizard. Please follow the instructions given. It is
recommended to keep the default parameters.
Option 2 can be used to install a FLACS license manager on a system not running FLACS. Alter-
natively one FLACS workstation in the network can be set up to serve licenses to all other FLACS
installations in the network.
The FLACS license manager must be set up before using FLACS. Please refer to section Setting
up the FLACS license server.
2.3.3 Setting up the FLACS license server
FLACS version 9.0 has a completely new license server/manager system, which operates through
a network protocol. This means that the license manager can be installed anywhere on the net-
work, as long as it is available to the FLACS clients through the local network. The license man-
ager can be installed locally on the machine where the FLACS simulation software is installed, or

separately from the simulation software. Only one license manager should be running on your
network, and this is where the FLACS license is installed. All other FLACS installations should
be set up using this license manager.
After the installation is finished, the FLACS license configuration utility should start automat-
ically. In the event that this does not happen please start the configuration utility as follows,
depending on your installation.
Linux:
> /usr/local/GexCon/FLACS_v9.0/bin/run configureWizard
Windows:
> C:Program FilesGexConFLACS_v9.0binconfigureWizard.exe
Alternatively it can be started from the FLACS Runmanager Help→Start Configuration Wizard.
If FLACS is installed system wide (installed as root), on Linux, the license manager must be
running as user root.
The configuration utility will guide you through the setup of the license manager. The config-
uration utility is also used to configure a FLACS installation that gets its license from a license
manager on a separate machine.
2.3.3.1 Setting up the license server on client only FLACS installation
If a FLACS license server is installed and running somehwere on the local network, the FLACS
installation must be configured to connect to the license server.
Figure 2.1: Setting up the license server on client only FLACS installation
2.3.3.2 Setting up the license server on a combined license server and client FLACS installa-
tion
If there is no FLACS license server available on the local network, a license server must be in-
stalled. To install a license server together with the FLACS simulation software, on the same

12 Getting started
machine, please use the following procedure. Alternatively a FLACS license server can be in-
stalled on a separate machine, with or without FLACS software. Please refer to section Stan-
dalone FLACS license manager installation.
Figure 2.2: Setting up the license server on a combined license server and client FLACS installa-
tion (steps 1 and 2)
Figure 2.3: Setting up the license server on a combined license server and client FLACS installa-
tion (steps 3 and 4)
2.3.3.3 Standalone FLACS license manager installation
It is possible to install the FLACS license manager only. This is useful if you would like to have
the license manager on a separate machine. To do this select the appropriate option during in-
stallation (see Software installation and setup).

To configure a standalone FLACS license manager prompt the license manager for an activation
key, by running the following command in a terminal window.
Linux:
> /usr/local/GexCon/FLACS_LicenseManager/bin/FLMserver --get-ActivationKey
Windows:
> C:Program FilesGexConFLACS_LicenseManagerbinFLMserver.exe --get-ActivationKey
Send the activation key together with the IP address and license manager communication port
number to <flacs@gexcon.com>.
The communication port defaults to 25001. Please make sure that this port is available, and open
on your system. If you are not sure about this please contact your system administrator.
GexCon will, based on the activation key, create a license text file. This file must be saved to:
Linux:
> /usr/local/GexCon/FLACS_LicenseManager/license/license-server.flm
Windows:
> C:Program FilesGexConFLACS_LicenseManagerlicenselicense-server.flm
Note that when using a standalone FLACS license manager, the license manager must be started
manually each time the computer is restarted. This can be done using a startup script (not pro-
vided).
2.3.3.4 Starting FLACS license manager as a service on Windows
The FLACS license manager can be started as a service on Windows using the following proce-
dure.
1. Verify that the FLACS License Manager is working properly as a desktop application
(a) FLACS software and license key must be installed (see procedure above)
(b) Test run FLMserver with the graphical user interface and then quit: > "C:Program
FilesGexConFLACS_LicenseManagerbinFLMserver.exe"
(c) Make sure to quit FLMserver, the service will not function if there is a desktop FLM-
server running.
2. Download and install the Windows Resource Kit (rktools.exe)
(a) See the following links about Windows Services and related tools:
• http://search.microsoft.com/results.aspx?mkt=en-US&setlang=en-US&q=rktools
• http://support.microsoft.com/kb/137890
3. Install the FLACS License Manager service "FLMserver" using INSTSRV:
(a) > instsrv FLMserver "C:Program FilesWindows Resource
KitsToolssrvany.exe"
(b) The service can be removed with > instsrv FLMserver REMOVE
(c) The path to srvany.exe might be different on your Windows installation

14 Getting started
4. Run REGEDIT to set up the details of the service
(a) It is strongly advised to backup your current registry before editing
(b) > regedit
(c) Locate and select the FLMserver key:
• "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesFLMserver"
(d) Add one new value for FLMserver: Description
• Edit→New→String Value : "Description"
• Description = "FLACS License Manager service."
(e) Add one new key for FLMserver: Parameters
• Edit→New→Key : "Parameters"
– Add two new values for FLMserverParameters: Application and AppParam-
eters
* Edit→New→String Value : "Application"
* Edit→New→String Value : "AppParameters"
* Application = "C:Program FilesGexConFLACS_-
LicenseManagerbinFLMserver.exe"
* AppParameters = –without-gui
* IMPORTANT NOTE: options start with double dashes: –without-gui
• The service will start automatically on reboot, it can also be started/stopped man-
ually:
– Control Panel→Administrative Tools→Services
2.3.4 Setting up the FLACS environment
After installation FLACS programs can be accessed from the system menu, in the following loca-
tions:
Linux (KDE): Start→Applications→Edutainment→Construction
Linux (Gnome): Applications→Other
Windows: Start→All Programs→GexCon→FLACS_v9.0
Some systems may require the user to log out and restart before FLACS will appear in the system
menu.
Desktops that do not follow the freedesktop.org standards will not install an icon in the Appli-
cations menu. This will happen on older distributions. In these cases, the user may be able to
install icons and associations manually. Refer to your GNU/Linux distribution vendor for details
on how to customize your desktop.
2.3.4.1 FLACS User setup on Linux
For easy access to FLACS from the command line add the following text to you startup file.
If you use the csh/tcsh shell, edit or create the .cshrc file:
alias run9 /usr/local/GexCon/FLACS_v9.0/bin/run
If you use the bash shell, edit or create the .bashrc file:
alias run9=/usr/local/GexCon/FLACS_v9.0/bin/run
FLACS programs can the be started by typing eg. run9 flowvis.

2.4 Running FLACS 15
2.3.5 Uninstalling FLACS
Linux: Run the program "/usr/local/GexCon/uninstall-GexCon.sh".
Windows: FLACS can be uninstalled using Control Panel/Add or Remove Programs.
2.4 Running FLACS
A typical simulation session with the CFD code FLACS involves several steps. Assuming FLACS
is properly installed on the computer, including valid lisence files for the software, users can
initiate a FLACS session by clicking the FLACS icon on the desctop:
Figure 2.4: The FLACS icon
This should open the Run Manager window:
Figure 2.5: The FLACS Runmanager
Some of the main tasks of the Run Manager are:
• Starting the Licence Manager
• Starting the preprocessor CASD
• Running CFD simulations

16 Getting started
• Starting the postprocessors Flowvis
The preprocessor should start when clicking the CASD icon in the Run Manager:
Figure 2.6: The CASD icon
The CASD window looks like this:
Figure 2.7: FLACS preprocessor CASD
Work in CASD often involves opening the Database window from the Geometry menu:
Geometry→Database
The Database window looks like this:

2.4 Running FLACS 17
Figure 2.8: Geometry database window
Typical tasks performed from the Database window include:
• Creating a new database and new geometries
• Opening existing databases and geometries
• Creating new materials (i.e. colours), or modifying existing materials
• Creating new objects, or modifying existing objects
The New Object button, available in the Objects tab in the Database window, opens the Object
window:

18 Getting started
Figure 2.9: CASD object window
The main purpose of the Object window is to construct a new object, or to modify an existing
object. Users can build complex objects by adding or subtracting several insides (i.e. boxes or
cylinders). Any geometry can consist of one or several objects, or assemblies of several objects.
An alternative way of working with geometries involves geometry import using the geo2flacs
utility . However, this requires that a representation of the geometry already exists on a compat-
ible CAD format (typically Microstation or PDMS).
Apart from geometry building, the menus in CASD also perform the following tasks:
• Definition of the computational domain and the computational grid
• Porosity calculations with the utility program Porcalc, as well as porosity verification
• Scenario setup, including:
– Definition of monitor point locations, and selection of output variables
– Specification of boundary conditions
– Specification of vent panels and leaks
– Specification of fuel type
– Specification of ignition position and time of ignition
After defining the scenario, the next step is to run the actual FLACS simulations:
• Simulations can be started and monitored with the run manager
• The same operations can be controlled from the command line in Linux
> run9 flacs 010100
Note that the Run Manager also monitors the simulations while they are running.

2.5 Help and support 19
The final step in a FLACS session is typically the presentation and verification of simulation re-
sults with the postprocessor Flowvis, as well as data extraction and reporting. The postprocessor
should start when clicking the Flowvis icon in the Run Manager:
Figure 2.10: The Flowvis icon
The Flowvis window looks like this:
Figure 2.11: FLACS postprocessor Flowvis
Some of the most frequently used features in Flowvis include:
• Verifying porosities in a geometry
• Creating scalar-time plots, 2D-plots, 3D-plots, ...
• Creating animations
Data reporting may also include the extraction of numerical simulation results with the utility
programs r1-file and r3-file. These programs run only from command line input in the current
version of FLACS.
2.5 Help and support
FLACS users can get technical support by contacting GexCon software department:

20 Getting started
Email: flacs@gexcon.com
Phone: +47 55574330
Commercial customers are entitled to support and maintenance:
Support: Up to 70 hours of email or phone support per year
Maintenance: New releases of FLACS as they are made available
In addition to the above the user has access to the FLACS User Group web site, which contains
information about FLACS, including a FAQ (Frequently Asked Questions) and a self support
portal where the user can search for answers (as of November 2008 GexCon is working on im-
plementing the self support portal, but a release date is not yet decided)
The support and maintenance requires the user to have a payed and valid support and mainte-
nance contract.
2.6 Introductory example
This chapter contains an introductory example. It gives a first impression of how to set up and
run a simple FLACS explosion simulation. For additional examples see sections Best practice
examples and Flowvis examples.
2.6.1 Things to keep in mind before you begin
FLACS is a CFD (Computational Fluid Dynamics) Explosion Simulator tool. The input to a CFD
calculation is:
• A geometry, either created manually for the specific purpose, or imported from a CAD
system
• A grid which divides the simulation domain into cells. In one cell a variable (eg. pressure)
does not vary in space. FLACS use a regular, Cartesian grid, which means box grid cells.
• Various scenario parameter, such as boundary conditions, monitoring point locations, gas
cloud size, position and composition, and ignition location.
All of the above is normally handled in the FLACS pre-processor CASD. The geometry is saved to
a file structure, called a file database. The file database file structure starts in a top level directory
given a name with suffix ".db". The file database should not contain user files, or files other
than those created by the file database interface in CASD.
In addition to the file database a number of other files are created before and during the simula-
tion. All files contains the job number, a 6 digit number. The following files are created as input to
the simulation (010101 is the job number).
cg010101.dat3 The grid file
cs010101.dat3 The scenario file
co010101.dat3 The geometry file. This file contains a snapshot of the geometry contained in the
file database.
cp010101.dat3 The porosity file, which is created by Porcalc. Please see section and Porcalc for
details.

2.6 Introductory example 21
During the simulation a set of result files will be created:
r1010101.dat3 Scalar-time output from monitor points
r3010101.dat3 Field output at selected times. Needed to create 2D and 3D plots
rt010101.dat3 Simulation log file
FLACS can also create and use other files. Please see section Files in FLACS for details.
Due to the number of files created by each simulation it is important to create a good file struc-
ture of directories to keep track of the files. See section Files in FLACS for details and further
recommendations.
2.6.2 Initialising the work directory
As FLACS creates a relatively large number of files it is important to have a good system for book
keeping. It is recommended to start out with an empty directory.
2.6.2.1 On Linux
Make a distinct directory (DIRECTORY_NAME) in which you perform the exercise:
> mkdir DIRECTORY_NAME
Move into this directory:
> cd DIRECTORY_NAME
Copy geometry files (notice the space before the ".").
> cp /usr/local/GexCon/FLACS_v9.0/doc/examples/ex2/*00001* .
Start up the FLACS runmanager:
> run9 runmanager
2.6.2.2 On Windows
1. Make a distinct directory in which you perform the exercise: Open the file browser ("My
Documents") and choose File→New→Folder.
2. Copy files from C:Program FilesGexConFLACS_v9.0docexamplesex2∗00001∗
(∗00001∗ means all files containing the text "00001").
3. Start the FLACS runmanager by clicking the desktop icon, or go to Start Menu→All
Programs→GexCon→FLACS_v9.0→FLACS Runmanager.
2.6.3 Initialising and starting the preprocessor CASD
Use Run Manager → Tools → CASD (or click the FLACS pre-processor icon)

22 Getting started
2.6.3.1 Open and view the geometry in CASD (Move cursor to the CASD window)
1. choose OPEN in the FILE menu OR ∗ file open <CR> OR ALT-f o (<CR> means carrige
return, ie. the enter key)
• CASD Ask for opening an existing job file
2. choose 100001.caj <OK>
• CASD: Open jobfile 100001, using MOUSE+LEFT
3. if any error message appears click <OK>
• CASD: Ignore error message => error message
• CASD: Play with visualisation options, fly through geometry etc.
Figure 2.12: The geometry used in example 1
2.6.3.2 Make a grid for the simulation
Make a grid (mesh) for the simulation, calculate porosities (module dim.: 25.6m x 8m x 8m, origin
in corner below the control room).
1. Choose SIMULATION_VOLUME from GRID menu
• CASD: To enter the extension of the simulation domain
2. Enter -16 <TAB> -8 <TAB> 0 <TAB> 40 <TAB> 16 <TAB> 16 <OK>
• CASD: Volume is defined (16m out from vent, 8m to the sides; observe - sign)

3. In GRID menu, choose DIRECTION X
4. In GRID menu, choose REGION and enter 56 <OK>
• CASD: 56 grid cells chosen (1.0m grid size).
5. Repeat steps for Y direction and use REGION 24
• CASD: 24 cells in Y-direction
6. Repeat steps for Z direction and use REGION 16
• CASD: 16 cells in Z-direction
7. In GRID menu, click INFORMATION, and <OK> to close window
• CASD: Check that grid dimension is 1.0m as intended
8. Choose SAVE from the FILE menu
• CASD: Save geometry and grid files
9. Choose CALCULATE from POROSITIES menu
• CASD: Map geometry information onto the grid, porcalc
10. Choose DISPLAY OFF in the GRID menus
• CASD: Don’t draw the grid anymore
Figure 2.13: Embedding the grid

24 Getting started
Figure 2.14: Porsity calculations using Porcalc
2.6.3.3 Define explosion scenario
1. Choose MONITOR_POINTS in SCENARIO menu OR ∗ scen mon <CR>
• CASD: Define where to measure variables
2. Click <ADD>, <EDIT> and 0.8 <TAB> 4.7 <TAB> 7.9 <OK>
• CASD: Add and define location of monitor point 1
3. Repeat this for point 2 (12.3, 4, 0.1) and point 3 (24, 7.9, 7.9)
• CASD: To edit a non-highlighted monitor, click on its number
4. Click <OK>
• CASD: Close MONITOR_POINT window
5. Choose SINGLE_FIELD_SCALAR from SCENARIO menu
• CASD: Define which variables to report at monitors
6. Click on <P>, drag mouse pushing MOUSE+LEFT across all monitors, <OK>
• CASD: Log pressure at all three transducers
7. Repeat for <PIMP> and <DRAG>
• CASD: Log pressure impulse and dynamic pressure, too
8. Click <OK> and choose SINGLE_FIELD_3D from SCENARIO menu
• CASD: Define variables for contour plots
9. Click on <P>, CTRL-<PROD>, CTRL-<VVEC>, <OK>
• CASD: Pressure, flame and velocity vectors. CTRL needed to select more than one
(NB! deselect when using the scroll bar)
10. Choose SIMULATION in SCENARIO menu OR ∗ scen sim <CR>
• CASD: Choose output and simulation parameters
11. Click on <NPLOT>, enter 50 <OK>, <OK>
• CASD: Increase number of contour plots, return to main menu
12. Click on GAS_COMP... in SCENARIO menu OR ∗ scen gas_c <CR>
• CASD: Define gas cloud loc., size, comp. and concentration
13. Click on <POS...>, 0 <TAB> 0 <TAB> 0 <OK>
• CASD: Position of bounding box describing gas cloud

14. Click on <DIM...>, 25.6 <TAB> 8 <TAB> 8 <OK>
• CASD: Dimension of gas cloud equals module dimensions
15. Click on <VOL...>, <METHANE> 91.7 <OK> <ETHANE> 7 <OK> <PROPANE> 1.3
<OK> <OK>
• CASD: Gas composition is defined
16. Click on <EQUI...> 1.05 <TAB> 0 <OK> <OK>
• CASD: Slightly rich gas mixture is chosen ER=1.05
17. Click on IGNITION in SCENARIO menu <POS...> 12.5 <TAB> 4.1 <TAB> 4.25 <OK>
<OK> OR ∗ scen ign pos 12.5 4.1 4.25 OK <CR>
• CASD: Define location of ignition (12.5, 4.1, 4.25)
18. Choose SAVE from the FILE menu
• CASD: Save all files, ready to run flacs
19. Minimize CASD
• CASD: Leave CASD for now, can be activated easily
Figure 2.15: Adding monitoring points

26 Getting started
Figure 2.16: Choosing variables for 3D output
Figure 2.17: Adding a gas cloud and choosing the gas composition

2.6.4 Start FLACS simulation
Select the job in Run Manager and click simulate (if job not visible, use add directory or if di-
rectory is already added, right click and rescan), check how the simulation starts up (click log
file)
Figure 2.18: Running a simulation in the FLACS Runmanager
2.6.5 Study results in post prosessor Flowvis
Use Run Manager → Tools → Flowvis (or click the FLACS post-processor icon)
1. choose ADD from Page menu (or CTRL+a)
• FLOWVIS: Prepare first page
2. click MOUSE+RIGHT, choose PLOT_TYPE and SCALAR_TIME plot
• FLOWVIS: Plotting of time histories of variables
3. choose 100001 and P with MOUSE+LEFT, select all 3 monitors (drag mouse) <OK>
• FLOWVIS: Plot pressure time history at all monitors
4. <RESCAN>
• FLOWVIS: if simulation is running rescan will update plot
5. Choose MODIFY in the Page menu (or CTRL+m), enter <TAB> 1 <TAB> 2 <OK>
• FLOWVIS: divide page into 2 plots
6. Click at lower frame, then MOUSE+RIGHT, PLOT_TYPE, ANNOTATION_ST (or CTRL+0)
• FLOWVIS: show numerical values from pressure plots

28 Getting started
7. ADD page and do the same for the DRAG and PIMP variables
8. Choose ADD in Page menu (or CTRL+a), click MOUSE+RIGHT, PLOT_TYPE, 2D... (or
CTRL+2)
• FLOWVIS: prepare 2D contour plot
9. Choose 100001, P, click <OK>
• FLOWVIS: contour plot of pressure
10. click MOUSE+RIGHT, choose PLOT_DOMAIN, change k-index to 5 <OK>
• FLOWVIS: choose XY-cut plane through ignition
11. Click MOUSE+RIGHT, choose VARIABLE_APPEARANCE change Value Range Setting to
Fixed
• FLOWVIS: choose a user-defined fixed scale for all time steps
12. Choose Min. Value as 0.05 and Max. Value as 2.0
• FLOWVIS: define the scale
Figure 2.19: Showing pressure-time curves with annotation in Flowvis

Figure 2.20: 2D cutplane plot showing over-pressures
Figure 2.21: Setting plot domain for a volume plot
Time steps can now be changed moving the bottom scroll bar to the right, page can be varied
using the right scroll bar.
1. Repeat this method for PROD and VVEC variables (these can be plotted on the same plot)

30 Getting started
• FLOWVIS: visualize flame and velocity vectors
Try to show PRESSURE and PROD on the same page using PAGE MODIFY (use a fixed scale
for PROD from 0.15 to 0.2 and change Min. Color Index to 9 and Max to 10) Now that you are
familiar with Flowvis, try the volume plot menu to study the development of flame (PROD) and
pressure Use PLOT DOMAIN to narrow the view window and see below the ceiling
2.6.6 Study the effect of ignition location
Enter CASD, open the 100001.caj job-file, save this as a new job number e.g. 100002.caj Change
ignition location in order to study how pressures may vary with different ignition locations End
ignition (0.5, 4.1, 4.25), (job number 100002) Your own assumed worst-case location (job number
100003)
Report highest pressure achieved on monitor point
Make animation of either 2D or volume plots using the export menu (with all timesteps)

32 CASD
The preprocessor CASD for the CFD simulator FLACS is used to prepare the input data, or job
data , that defines a FLACS simulation: geometry model, computational grid, porosites, and
scenario description. CASD is an acronym for Computer Aided Scenario Design.
CASD 4 released in 1994, use X11 graphics, but a new version is available based on QT
CASD 5 released in 2001, use Open Inventor graphics
CASD 6 released in 2008, use QT and Coin 3D graphics
This manual describes CASD 6, but the general functionality of CASD 6 is in principle the same
for CASD 4 and CASD 5. CASD 6 is fully backward compatible with CASD 4 and CASD 5.
3.1 Overview
This section provides a general overview of the functionality in CASD.
3.1.1 Starting CASD
Users start CASD by clicking the CASD icon in the run manager window:
Figure 3.1: The CASD desktop icon
or alternatively by executing the command:
> run9 casd6
on the command line in Linux.
3.1.2 CASD command line options
The following options can be given when starting CASD on the command line:
Option Description
-macro macro file name Read input from specified macro file
-numMat maximum number of materials Default is 50
-numObj maximum number of objects Default is 10000
-numAsis maxmimum number of
assemblies/instances
Default is 3500
-stackAsis maxmimu number of nested assembly
levels
Default is 8
-noLock Turns of locking on the database files. Must
not be used if more than one user accesses the
database simultaneously. This option speeds
up the database operations significantly.

3.1 Overview 33
-display and others Linux: options accepted by X
Table 3.1: CASD command line options
Example:
Linux:
run9 casd -numObj 20000 -numAsis 20000 -noLock
Windows:
casd -numObj 20000 -numAsis 20000 -noLock
Alternatively the options can be set permanently in the FLACS Runmanager,
Options→Preferences. This will only apply if CASD is started from the Runmanager.
3.1.3 The main window in CASD
Starting CASD 6 opens the main window.
Figure 3.2: The main window in CASD
The main window is divided into the following parts:
• The menu bar

34 CASD
• The icon bar
• The command input field
• The geometry window(s)
• The status field
These parts are described in the following subsections.
3.1.4 The menu bar
The menu bar contains the following menus:
• File
• Geometry
• Grid
• Porosities
• Scenario
• Block
• View
• Options
• Macro
• Help
The options on the various menus are described in separate sections in this chapter.
3.1.5 The icon bar
The icon bar contains the following toolbars:
• Main toolbar, provides shortcuts to several of the commands on the meny bar:
– New, Open, Save, Save as, Import, and Result on the File menu.
– Database icon on the Geometry menu.
– Calculate and Verify porosities on the Porosity menu.
• Graphics toolbar, controls various features of the geometry window(s).
– View splitting.
– Rectangle zoom.
– Spinning (toggle on/off).
– Highlighting option, from filled only (0) to various degrees of contour highlighting
(1-5).
• Drawing toolbar, opens the plan drawing dialog box:
– Specifying file names for texture (e.g. drawings).
– File formats: PNG, JPEG, GIF, TIFF

3.1 Overview 35
3.1.6 The command input field
The command input field represents an alternative interface between the user and CASD, in
addition to the regular menus on the menu bar. The control input field contains a scrollable
command history list, and a current command context indicator (left side). The user controls the
command history list from the keyboard:
• UP: retrieves the previous line from the command history list
• DOWN: retrieves the next line from the command history list
• RETURN: processes the content of the command input field
Hence, the user can choose whether to use a menu options on the menu bar, e.g: File→Exit→Yes
(to exit and save) or to execute, after typing or retrieving, the following command in the com-
mand input field:
∗ file exit yes yes Command line input will in many situations be the most efficient way
to work with CASD, and other sections in this chapter present additional examples on how to
use this feature.
Examples: Using the command input field in CASD
• Select a box primitive in an object. The following command moves the box to (2, 2, 2), and
would cause the properties dialog to be shown
– ∗ edit properties 2 2
– This is because the position is not completely specified. The user does not have to
specify all parameters, but must include all values for the parameter specified.
• If the user wants to edit one of the last parameters in the dialog, it is not necessary to specify
all the parameters in front. The parameter name can be used to indicate which parameter
to edit
– ∗ edit properties size 2 2 2 vol_por 0.5
• The user can also supply the answer to a question in the input field. To delete an assem-
bly/instance, CASD will ask to confirm the operation. To avoid the question dialog, type
the following command
– ∗ geometry delete yes
– or shorter: ∗ ge de y
• To direct the output from a list to a file, append the file name after the list command. For
instance, to list geometries in the database, enter the following command, which will create
the text file outfile.txt
– ∗ geometry list outfile.txt
3.1.7 The graphical area
The graphical area in the main window displays the geometry and the computational grid. In
addition to the options on the View menu, there are several ways of manipulating the view:
• Rotation: MOUSE+LEFT
• Panning: CTRL+MOUSE+LEFT
• Zoom: MOUSE+SCROLL
• Rectangle zoom: MOUSE+RIGHT+SELECT

36 CASD
• Splitting and closing views: MOUSE+RIGHT+SELECT
The use of these features are quite intuitive, and they will not be described in more detail in this
manual.
3.1.8 The message area
The message area in the main window contains information concerning the active database,
project, geometry, grid, and units.
3.1.9 Files in CASD
CASD stores job data on a set of files. For the arbitrary job number 010100, the most important
files are:
• Header file, 010100.caj: ASCII file created by CASD; defines the co, cg, and cm files used by
CASD.
• Geometry file, co010100.dat3: binary file created by CASD; contains a list of primitives from
a CASD database that define the geometry; used by Porcalc and Flowvis.
• Grid file, cg010100.dat3: binary file created by CASD; defines the computational mesh; used
by CASD, Flacs, and Flowvis.
• Porosity file, cp010100.dat3: binary file created by Porcalc (typically from the Grid menu in
CASD); defines the porosities for each grid cell; used by Flacs and Flowvis.
• Polygon file, cm010100.dat3: binary file created by CASD; defines the polygon model; used
by Flowvis (if the file exists).
• Scenario file, cs010100.dat3: ASCII file created by CASD; defines the general scenario (mon-
itor points, output variables, fuel region, pressure relief panels, ignition position, etc.); used
by CASD, Flacs, and Flowvis.
The grid-file is also called the obstruction file, or co-file, and is not a direct input to the simulation; it
is however used by Porcalc when generating the porosity file. The File menu in the main window
contains commands for creating, opening, and saving the various job files. See section Files in
FLACS for further information.
3.1.10 Working with geometries in CASD
To implement the geometry model in CASD can often be the most time consuming part of a
project. For modern process facilities it may be possible to import a geometry from an existing
CAD model, but for many installations the geometry must be constructed manually from draw-
ings, photographs, etc.
A large projects, such as a full probabililistic analysis, can involve hundreds of CFD simulations,
and each simulation will typically produce 10-15 different files. Hence, it is very important to
organize the files in a well-structured manner.
The building blocks in a CASD geometry are instances of objects. The structure within an object
is a so-called Constructive Solid Geometry (CSG) model, where simple solid primitives (boxes
and cylinders) are combined by Boolean operators (unions and left differences).
Objects in CASD can be either global or local. Several geometries can contain instances of the
same global object, whereas a local object can only be included in the geometry where it was
created. It is generally recommended to use global objects, and avoid the use of local objects.

3.1 Overview 37
The list of information required to implement a typical process facility, such as an offshore oil
platform or an onshore process plant, is quite extensive:
• Plot plan
• Sectional drawings
• Piping plan
• HVAC layout
• Cable trays layout
• Framing plans
• Cladding
• Deck plan
Most FLACS users find it convenient to define standardized axis directions, and the following
convention is used by GexCon for typical process facilities:
• East-West along the x-axis, with positive x towards the east.
• North-South along the y-axis, with positive y towards the north.
• Up-Down along the z-axis, with positive z pointing upwards.
This results in a conventional right handed coordinate system, where the lower south-western
corner of the facility coincides with the origin (0,0,0).
Each object in a CASD database is assigned a material property, and each ’material’ is assigned a
colour hue from the 0-360° colour circle. Many FLACS users find it convenient to assign certain
hues to various structural elements, and the following convention is used by GexCon for typical
process facilities.
Hue Colour Description
0 Red solid walls and decks
30 Orange pressure relief and and
louvred panels
60 Yellow grated decks
120 Green anticipated congestion
180 Cyan equipment
200 Light blue structure
220 Medium Blue secondary structure
250 Dark Blue piping
300 Pink equipment
Table 3.2: Colour convention used by GexCon
A standardized colour scheme makes it more straightforward to review geometries from old
projects.
3.1.11 About congestion, confinement, and vents
In order to have a good representation of the effect of obstacles it is important that they are well
represented geometrically by the chosen grid. In most practical situations it will not be possible
to represent the smaller obstacles on the grid, these should still be included since they may be
treated by proper sub-grid models. Larger obstacles like the floor (or the ground), the ceiling, the
walls and larger equipment will be resolved on-grid. This means that they will be adjusted to
match the grid lines.

38 CASD
The most challenging geometry to represent properly is repeated obstacles of the same size and
spacing as the chosen grid resolution, in such cases the user should consider to change the grid to
achieve a better representation. If this type of geometry is dominant it is of vital importance for
the accuracy of the result that the representation is good enough. In cases where such a geometry
is not dominant one may pay less attention to how it is represented. For normal offshore modules
there will be a range of subgrid sized obstacles which are more or less randomly distributed in
space.
In many experimental setups one will find repeated obstacles of the same size. The basic research
on gas explosions past many years now has focused on the effect of obstacle arrays, perhaps to
a greater extent than on the effect of more realistic geometries. Both categories are important in
order to be able to validate tools like FLACS.
It is important to represent the vent openings of a semi-confined geometry properly. If obstacles
close to the outer boundaries are adjusted to match the grid, the effective vent area may be af-
fected. In order to verify that the representation of the vent openings is as good as possible the
user should check the porosity fields (using CASD or Flowvis).
3.2 File menu
3.2.1 New
Shortcut CTRL+N
Starts a new simulation job.
The New command in the File menu creates a new empty job. If there were unsaved changes to
the current job, a dialog box is displayed, asking about saving the changes.
3.2.2 Open
Shortcut: CTRL+O
This command opens an existing set of simulation files. The default selection is defined in a ∗.caj
file.
The Open command in the File menu opens an existing job.
If you enter the file name in the command input field, the path must be encapsulated in apostro-
phes, for instance:
∗ open "../../Test/000000.caj"
If you select the command from the menu bar, or if no name is specified in the command input
field, the Open dialog box is displayed, allowing you to specify a path and file name to open.
By default, the file filter is initiated for selecting CASD job header files (type ∗.caj). But you
may also select a geometry file (type co∗.dat3). CASD will then open all files with the same job
number.
If a geometry is open (in the database), the filter string will be constructed from the project and
geometry numbers. It is not possible to open a job that is not compatible with the open project
and geometry numbers.
If there were unsaved changes to the current job, a dialog box is displayed, asking about saving
the changes.
The geometry file is not read when a geometry is open in the database. If no geometry is open

3.3 Geometry menu 39
in the database, CASD will display the contents of the geometry file in the graphic area after
successful open. The contents of the geometry file can be edited using the Edit File command in
the Geometry menu, see section Geometry menu.
3.2.3 Save
Shortcut: CTRL+S
Saves the current simulation job (i.e. the various files that define the job).
The Save command in the File menu saves the current job.
3.2.4 Save as
Shortcut: CTRL+SHIFT+S
The Save As command saves the current job under a new (user-defined) name (job number).
3.2.5 Import
Imports certain specifications from another simulation job (e.g. grid file, scenario file, etc.).
3.2.6 Exit
Shortcut: CTRL+Q
Exits the CASD software.
3.3 Geometry menu
CASD stores the geometry in a database, and on the geometry file (co-file). The commands in
the Geometry menu in the main window, except the Edit File command, are available when
connected to a database. The Save and Save As commands in the File menu writes the geometry
to the geometry file.
The building blocks in a CASD geometry are instances of objects. Objects can be global or local.
Several geometries can contain instances of the same global object, while a local object only can
be included in the geometry where it was created.
Instances can be grouped under assemblies. Several levels of assemblies can be created. Each
instance and assembly has a transformation matrix. The position, scale, and orientation of an
instance is the result of the matrices on all levels above the instance, in addition to the matrix for
the instance itself.
Each geometry is a member of a project. The project is the top level in the CASD data structures.
A project can own a number of geometries.
Instances and assemblies can be made invisible and visible using the following commands:
CTRL+I Make the selected assembly/instance invisible
CTRL+SHIFT+I Make the selected assembly/instance visible.

40 CASD
Use the Position command in the Geometry menu to change the position of the selected assembly
or instance.
3.3.1 Geometry Database
The first option on the Geometry menu in CASD opens the Database dialog box.
Figure 3.3: The geometry database window in CASD
In the Database dialog box the user can:
• Create a new database, project, geometry, or object.
• Connect to or save an existing database.
• Open or save existing, projects, geometries, or objects.
• Insert instances in a geometry.
• Define new materials or edit existing materials.
3.3.1.1 Geometry tab
On the Geometry tab the user can create, open and manipulate projects and geometries. Projects
can be renamed and deleted, geometries can be renamed, copied and deleted.
3.3.1.2 Objects tab
The New Object button in the Database dialog box opens the Object window.
3.3.1.3 Materials tab
Each object in a CASD database is assigned a material property, and each ’material’ is assigned
a colour hue from the 0-360° colour circle. To define a new material click the New Material
button. The new material is defined by a name and a hue, a value between 0 and 360.

3.3.2 Creating a CASD database
To create a database choose Geometry→Database or type ∗ geometry database. The Geome-
try Database window is shown. Click the Connect button. A file selection dialog box is displayed.
Move to the directory where the database should be created, and write the name of the database,
e.g. my_database.db. Alternatively the database can be created using the command input: ∗
database create my_database.db, which will create a database in the current directory.
If the Geometry Database window is not open, choose Geometry→Database. Use the New Project
button to create a new project, or the Open Project button to open an existing project.
When a project is opened, a new geometry can be created clicking the New Geometry button, or
open an existing geometry clicking the Open Geometry button.
When an existing geometry is opened, the assembly/instance structure and all objects and
materials used are loaded into the CASD program. If the geometry contains many assem-
blies/instances, you may get an error message indicating that there were not room enough in
the CASD data structures. See section CASD command line options for information on how you
can use command line options to allocate more memory for these structures.
3.3.3 Connecting to a database
To create a new database, see section Creating a CASD database.
To connect to an existing database choose Geometry→Database or type ∗ geometry
database. The Geometry Database window is shown. Click the Connect button. A file se-
lection dialog box is displayed. Select the CASD_DB file on the database directory you want to
connect to.
If you enter the file name in the command input field, the path must be encapsulated in apostro-
phes, for instance:
∗ database connect "MyCasdDB/CASD_DB"
3.3.4 Creating a new or opening an existing object
You can create a new object clicking the New Object button on the Objects tab in the Geometry
Database window, or open an existing object using the Open button.
When you have completed the New or Open Object command, the object window is displayed.
3.3.5 Selecting a node and a subtree
At any time, a part of the binary tree is selected. It may be a single node, or a subtree containing
several nodes. If a subtree is selected, the top node is referred to as the selected node. In the
postfix string, the top node is the rightmost node in the subtree.
The selected subtree is highlighted in the graphic window, and underlined in the message area.
There are two different methods for selecting a subtree.
1. Click MOUSE+LEFT while pointing at a primitive. If several primitives are hit, they are
placed on a stack (list). Only one primitive is selected at a time. Press CTRL+TAB command
to parse this stack.
2. Use the following commands:

42 CASD
CTRL+L Select the previous instance
CTRL+R Select the next instance
3.3.6 Maintaining a CASD database
The dbfutil program is available for creating and maintaining CASD file databases.
Linux:
run9 dbfutil database command [option]
Windows:
dbfutil database command [option]
The usage of this program is described in table Using the the dbfutil program. Make sure that no
other users are connected to the database when you execute this program.
Command Description
create Create database
destroy Destroy database
force Destroy database, override any errors
dellock Delete all locks. Use this command if files in
the database are still locked after a crash in
CASD
restoredep Restore dependencies. For each object in the
database, there is a file containing a list of all
geometries that contain instances of the
object. (Executing the Information command
in the File menu in the Object dialog lists the
contents of this file.) This file is used for
determining if the object can be deleted
when you execute the Delete Object
command in the Database menu. CASD
updates these files when required. But if a
problem should occur for some reason, the
restoredep command might help. It updates
the file mentioned above for all objects in the
database.
restorehead Restore header files. This command resets
the process log file for the database. This file
contains a list of (CASD) processes currently
connected to the database.

list List the content of all table files, e.g. list O
lists all objects:
P List the content of all project table files.
O List the content of all object table files.
M List the content of all material table files.
G List the content of all geometry table files.
L List the content of all local object table
files.
U List the content of all objects-used table
files.
A List the content of all asis table files.
Table 3.3: Using the dbfutil program
We strongly recommend that you make backups of your databases on a regular basis.
3.3.7 Local objects
Local objects consist simply of one box or one cylinder. Use local objects to define entities like
walls, floors etc. Define global objects for more complicated things.
The name of a local object must start with an underscore character (_).
The Local Object command in the Geometry menu creates a local object, and one instance of it.
You can of course create several instances of the local object using the Instance command.
The Local Object command has two sub choices, Box and Cylinder. Select the appropriate primi-
tive type.
CASD will first ask for the material name. Enter the name of an existing material. The material
decides the colour of the object. If you haven’t defined any materials, use the New Material
command in the Geometry Database window to create one.
CASD will then ask for the sizes and porosities for the primitive. CASD creates an instance of the
object in (0, 0, 0). Use the Position or Translate command to move it to the correct position.
You can use the Properties command to edit material, sizes and porosities for a local object. The
Rename command changes the name of the object.
3.3.8 Global objects
A global object is edited in a separate object window. All the commands described in this chapter
refers to the menus in the object window.
Global objects can have instances in several geometries. The structure within a global object is a
constructive solid geometry (CSG) model where simple solid primitives are combined by means
of Boolean set operations. The primitives and operations are nodes in a binary tree where the
leaves are primitives and the internal nodes are operations.
Boxes, cylinders, ellipsoids, general truncated cones (GTC) and complex polyhedrons (CP8) are

44 CASD
the primitive types supported. The box primitive includes planes as a special case. Available
operation types are union and difference.
Warning:
Only boxes and cylinders should be used in by default, but ellipsoids, general truncated
cones and complex polyhedrons can be used in special cases. These latter primitive types
have the following important limitations:
• No subgrid models, thus not contribution to turbulence and drag force
• Porosity calculation takes a long time for these primitive types. There should be no
more than 100-200 of these primitives in any given geometry
Figure 3.4: Supported primitive types
A root is a subtree that is not part of another subtree. The object typically contains several roots
during editing. But it must contain only one root when it is saved.
The postfix string represents a way of visualising the binary tree defining the object.
The postfix string for the open object is displayed in the message area in the object window. The
selected subtree is highlighted.
A material is assigned to each object. The material decides the colour of the object.

Figure 3.5: The binary tree for an objects, and the corresponding postfix string
3.3.9 Assembly
Opens a dialog box where the user can specify an assembly of several instances.
3.3.9.1 Adding an assembly
Assemblies represents a way to group the instances in complicated geometries. The Assembly
command in the Geometry menu adds an assembly to the geometry. CASD will ask for the
assembly name. You must enter a name that doesn’t exist on the same level, see below. The
assembly is placed in (0, 0, 0). You can transform an assembly in the same way as an instance.
All geometries contains at least one assembly, called the top assembly. That assembly can not be
deleted.
When you create an assembly, it is placed in the geometry structure depending on what was
selected on forehand. If an instance was selected, the new assembly is placed after that instance
under the same assembly. If an assembly was selected, the new assembly is placed under that
assembly.
You can later rename the assembly using the Rename command.
3.3.9.2 Selecting an assembly or instance
The selected instance, or all the instances in the selected assembly, are highlighted in the graphic
window. The name of the selection is written in the message area. The name is concatenated
from the geometry name, the names of all assemblies above the selected assembly/instance, and
the name of the selected assembly/instance. Each level is separated by a period (.). An example
is shown below.
Current Geometry Selection: M24.A1.COOLER-2

46 CASD
Here, M24 is the geometry name, A1 is an assembly. The last part of the string is the lowest
level. In this example, it is an instance, identified by the object name, COOLER, and the instance
number.
There are three different methods for selecting an assembly or instance. The first method is to
select from the graphic window. To do this, click MOUSE+LEFT while pointing at the instance. If
several instances are hit, they are placed on a stack. Only one instance is selected at a time. In
CASD4 use the CTRL+TAB command to parse this stack.
The second method is to use the following commands:
• Select the parent assembly: Press CTRL+U.
• Select the child assembly/instance: Press CTRL+D.
• Select the assembly/instance name: Press CTRL+F. You are asked to enter the concatenated
name to select.
• Select the previous assembly/instance on the same level: Press CTRL+L.
• Select the next assembly/instance on the same level: Press CTRL+R.
The third method is to use the List command in the Geometry menu to pop up a list of the
contents of the open geometry. You can use the mouse to select from the list.
3.3.10 Instance
Creates an instance in the current geometry and/or assembly.
3.3.10.1 Adding an instance
To add an instance of an object, use the Instance command in the Geometry menu. CASD will
ask for the object name. You must enter the name of an existing object. The instance is placed in
(0, 0, 0). Use the Position or Translate command to move it to the correct position.
Alternatively the Instance button on the Objects tab in Geometry Datbase dialog can be used.
When a new instance is created, it is placed in the geometry structure depending on what was
selected on forehand. If an instance was selected, the new instance is placed after that instance
under the same assembly. If an assembly was selected, the new instance is placed under that
assembly.
3.3.11 Local object
Creates a local object in the current geometry.
3.3.12 Delete
Deletes either the currently selected instance, local object, or the current assembly (must be
empty).
3.3.13 List
Lists all assemblies and instances in the current geometry, including modified positions.

3.3.14 Duplicate
Duplicates the selected instances in the current geometry.
3.3.15 Position
Defines the position of an instance.
3.3.16 Translate
Translates the current instance.
3.3.17 Rotate
The Rotate command rotates the selected assembly or instance. Note that CASD only accepts axis
parallel geometry. That means that the rotation angle must be a multiples of 90 degrees.
3.3.18 Scale
Scales the current instance by a certain factor in each spatial direction
3.3.19 Matrix
Specifies the transformation matrix of the current instance. This command is normally not used
directly, but is available for macro reading and writing.
3.3.20 Making an assembly or instance visible or invisible
Shortcut: CTRL+I CTRL+SHIFT+I
This command lets the user make the current instance invisible/visible.
3.3.21 Select
Selects an instance in the current geometry through the following short cut options. See section
Selecting an assembly or instance.
3.3.22 Substitute
Substitutes all instances of one object in the current geometry with instances of another object.
The user specifies the name of the existing object and new objects.
3.3.23 Properties
Opens a dialog box where the user can observe and edit the properties of a local object.

48 CASD
3.3.24 Rename
Opens a dialog box where the user can rename assemblies or local objects.
3.3.25 Object
Opens the currently selected object.
3.3.26 Edit file
The Edit File command in the Geometry menu makes it possible to edit the geometry file (co file)
for the open job. This command is only available when no geometry is open in the database.
The geometry is saved on the geometry file as one single object, when selecting Save in CASD.
Upon the Edit File command, an object window is therefore shown for editing this object, if
the geometry database is not available, or the user wants to make small modifications to the
geometry outside of the database.
Since the object structure lacks the assembly/instance mechanism, editing the geometry file di-
rectly without using the database is recommended only for geometries with a relatively small
number of primitives. For geometries with many primitives, the postfix string is long and diffi-
cult to manage.
Editing the geometry file for FLACS simulations may be advantageous when the user want to
test the impact of small changes in the geometry on the simulation results. Note that there is no
way to update the database from the geometry file.
3.4 Object window in CASD
The object window opens from the ’New Object’ button in the database dialog box.
The object window opens from the database window.

3.4 Object window in CASD 49
Figure 3.6: The object window in CASD
The message area in the object window shows the postfix string.
3.4.1 File menu in the Object window
The options on the file menu in the object window are explained below.
3.4.2 Save
If the user is editing an object in the database, the Save command in the File menu saves the object
on the database.
If the user is editing the geometry file, the changes are stored internally in the geometry database,
and will be written to the file upon the Save and Save As commands in the File menu in the main
window. Exiting from the object window without saving, the changes are lost.
The object is stored only if it is consistent, that is if it has only one root. If the object is not
consistent, an error message is displayed, and a Union or Left Difference should be added.
3.4.3 Information
The Information command in the File menu displays a list of all geometries containing instances
of the open object.

50 CASD
3.4.4 Exit
Upon the Exit command, CASD asks about saving the object, and then whether to exit from the
object. If the answer is yes to the last question, the object window is closed.
3.4.5 Edit menu
The options on the edit menu in the object window are explained below.
3.4.5.1 Operations
The Operation command in the Edit menu changes the operation type if the selected node is an
operation.
3.4.5.2 Properties
The Properties command in the Edit menu changes the primitive properties if the selected node is
a primitive.
If you have selected a subtree containing only one type of primitives, the Properties command can
be used for changing one or more parameters for all these primitives.
3.4.5.3 Translate
Use the Translate command to translate the selected assembly or instance a specified distance in
each axis direction.
Use the Translate command in the Edit menu to translate the selected subtree a specified distance
in each axis direction.
3.4.5.4 From To
Use the From To command to translate the subtree so that one specified position, the base point,
is moved to another, the target point. A dialog box for specifying the two positions is displayed.
A circle is displayed in the graphic window, indication the position being edited. CASD keeps a
list of positions used in the object. By pressing CTRL+L or CTRL+R, you can parse this list. The
coordinates in the dialog box is updated.
3.4.5.5 Rotate
The Rotate command rotates the selected subtree. You must specify a base point for the rotation,
and the rotation angle. As for the From To command, you can parse the position list using the
CTRL+L or CTRL+R commands. Note that CASD only accepts axis parallel geometry. That means
that the rotation angle must be a multiple of 90 degrees.
3.4.5.6 Scale
The Scale command is only legal when an instance of a local object consisting of a box is selected.

The Scale command scales the selected subtree. You must specify a base point for the scaling,
and the scaling factor. You can parse the position list using the CTRL+L or CTRL+R commands
3.4.5.7 Delete
The Delete command in the Edit menu deletes the last node in the postfix string, the selected
subtree or the current root. Note that if the postfix string for the object is consistent, it consists of
only one root. Therefore deleting the current root deletes the entire object.
3.4.5.8 Mark
The Mark command is used in connection with the Substitute command. Select Mark command
to mark the subtree to be substitued with the subtree selected when the Substitute command is
selected.
3.4.5.9 Substitute
The Substitute command in the Geometry menu substitutes all instances of one object with in-
stances of another object. You are asked to specify the two object names.
The Substitute command in the Edit menu substitutes the selected subtree with another subtree.
Use the Mark command to select the first subtree.
The substitute command implies the following steps. (Let subtree 1 denote the first subtree and
subtree 2 the second subtree.)
1. Make a copy of subtree 2 and give it a new identity, say subtree 3.
2. Delete subtree 1 from the postfix string.
3. Insert subtree 3 in the postfix string in the position where subtree 1 was situated.
3.4.5.10 Duplicate
The Duplicate command in the Geometry menu duplicates the selected instance. You are asked
to enter the number of copies, and the distance between each copy in the three axis directions.
Click on Ok, and a dialog box pops up for each copy, allowing you to edit the position.
The Duplicate command in the Edit menu duplicates the selected sub tree. You are asked to enter
the number of copies, and the distance between each copy in the three axis directions. Union
operations are added automatically, so that the resulting sub tree includes the original one.
Creating pipe bundles Start with creating one cylinder with the appropriate diameter, length
and direction. Use the Duplicate command in the Edit menu to duplicate the cylinder in one
direction. Use the same command once more to duplicate the resulting row of cylinders in the
other direction.
If you need to change some parameters for all the cylinders, select the entire pipe bundle sub tree
and use the Properties command. If you want to change the distances between the cylinders, this
can be done by scaling the entire sub tree. Afterwards you can use the Properties command to
reset the cylinder diameters and lengths.

52 CASD
3.4.5.11 Material
The Material command in the Edit menu edits the material name for the object. You must enter
an existing material name.
3.4.5.12 Matrix
The Matrix command was introduced to make it simple to create and run macros for creating
geometries.
Warning:
This command should normally not be used in interactive mode.
3.4.6 Add menu in the Object window
The options on the add menu in the object window are explained below.
3.4.6.1 Box
The Box command in the Add menu adds a box at the end of the postfix string. A dialog box for
defining the box parameters is displayed.
3.4.6.2 Cylinder
The Cylinder command adds a cylinder at the end of the postfix string. A dialog box for defining
the box parameters is displayed.
3.4.6.3 Ellipsoid
The Ellipsoid command adds an ellipsoid at the end of the postfix string. A dialog box for defining
the ellipsoid parameters is displayed. Note warning about the use of ellipsoid.
3.4.6.4 CP8
The CP8 command adds a complex polyhedron at the end of the postfix string. A dialog box
for defining the complex polyhedron parameters is displayed. Note warning about the use of
complex polyhedron.

Figure 3.7: Definition of a complex polyhedron
3.4.6.5 GTC
The GTC command adds a general truncated cone at the end of the postfix string. A dialog box
for defining the general truncated cone parameters is displayed. Note warning about the use of
general truncated cone.
Figure 3.8: Definition of a general truncated cone
3.4.6.6 Union
The Union command adds an union operation at the end of the postfix string. This command is
only legal if the object contains at least two roots which can be connected by the operation.
3.4.6.7 Left Difference
The Left Difference command adds a difference operation at the end of the postfix string. This
command is only legal if the object contains at least two roots which can be connected by the
operation. If using CASD4, use the Shade command in the View menu, to see the result of the
operation. Note that the right hand side operator of a difference operation must be a primitive.
3.4.6.8 Copy
The Copy command adds a copy of the selected sub tree at the end of the postfix string.

54 CASD
3.4.6.9 Object
The Object command adds a copy of a specified object at the end of the postfix string.
3.4.7 Select menu in the Object window
The options on select file menu in the object window are explained below.
3.4.7.1 Previous
Shortcut: CTRL+L
Selects the previous primitive or subtree
3.4.7.2 Next
Shortcut: CTRL+R
Selects the next primitive or subtree
3.4.7.3 Stack
Shortcut: CTRL+TAB
This command will parse (cycle through) the list of selected primitives or subtrees if more than
one is selected.
3.4.8 View menu in the Object window
The options on the view menu in the object window are explained below.
3.4.8.1 Print
The Print menu allows exporting a screenshot of the CASD window into different formats:
• Postscript
• RGB
• IV
3.4.8.2 Examiner Viewer and Fly viewer
The default and most widely used viewer is the Examiner viewer. The Fly viewer can be used to
fly through the geometry.
3.4.8.3 The XY, XZ and YZ views
The option XY View and XZ View display a projection of the geometry in the XY and XZ planes
respectively. The options YZ East View and YZ West View display a projection of the geometry
in the YZ plane along the positive and negative Y-axis respectively.

3.4.9 3D View
The 3D View option displays a default 3D view of the geometry.
3.4.9.1 Axis
The Axis option turns axis display on and off.
3.4.9.2 Maximize
The option Maximize maximizes the visible window to display the entire geometry and grid.
3.4.9.3 Grid Display
Three different options are available in the Grid Display menu:
• Off: The grid is not displayed. Only the geometry would be displayed.
• Working Direction: The grid would be displayed in the working direction only.
• All Directions: The grid would be displayed in the three directions.
3.4.9.4 Annotation
The options in this menu are currently not used.
3.4.9.5 Draw Style
Different options are available in this menu:
• Off: The geometry will not be displayed.
• Wireframe: Only the edges of the objects that compose the geometry would be displayed.
• Filled: Surfaces of the objects that compose the geometry would be displayed.
• Scenario Wireframe: Only the edges of scenario objects (for example, a fuel region) would
be displayed.
• Scenario Filled: Surfaces of scenario objects would be displayed.
3.4.9.6 LOD and Properties
The LOD (Level Of Details) and properties menus control the details of the geometry displayed.
3.4.10 Macro menu in the Object window
The options on the macro menu in the object window are explained below. for more infromation
about CASD macros see section Macro menu.
3.4.10.1 Run
Read a macro file defining a single object.

56 CASD
3.4.10.2 Record
Writes all commands given to a user specified macro file.
3.4.10.3 Write Object
Writes a macro file containing the current object.
3.5 Grid menu
The simulation volume is divided into a set of control volumes by three sets of grid planes, one
in each axis direction.
There is always a current grid working direction, and a selected region of grid planes in this
direction. The current working direction is shown in the message area. The lines indicating the
selected region is highlighted.
3.5.1 Simulation volume
The Simulation Volume command lets you change the simulation volume extent in all three di-
rections. If you increase the volume, the original grid planes are kept, but one additional plane is
added in each direction. If you decrease the volume, planes outside the new volume are deleted,
and new planes are created on the volume borders.
3.5.2 Direction
The Direction command changes the working direction. Legal input is x, y or z. The Grid menu
commands Region, Add, Position, Move, Delete, Smooth, Stretch and List affects the grid planes
in the working direction.
3.5.3 Region
The Region command substitutes the selected grid planes by a new set of grid planes. CASD asks
you to enter the new number of control volumes in the region.
3.5.4 Add
The Add command adds a new grid plane in the working direction. You are asked to enter the
coordinate value for the new plane.
3.5.5 Position
The Position command lets you edit the position for the selected grid plane.

3.5 Grid menu 57
3.5.6 Move
The Move command moves the selected grid planes a specified distance.
3.5.7 Delete
The Delete command deletes the selected grid planes.
3.5.8 Smooth
The Smooth command substitutes the selected grid planes by a new set of grid planes.
For the Smooth command, the sizes of the control volumes at each end of the region is kept
unchanged. The sizes of the control volumes between them varies gradually.
This function is typically used when refining the grid around a leak.
3.5.9 Stretch
The Stretch commands substitutes the selected grid planes by a new set of grid planes. This is
particularly useful when stretching the grid towards the outer boundaries.
The Stretch command has two sub-choices:
• Negative Direction (typically used at the boundaries at the negative end of the axis)
• Positive Direction (typically used at the boundaries at the positive end of the axis)
You must enter the size of the control volume at one end of the region, default is the current size.
Then you must enter a factor by which the sizes of the control volumes in the specified direction
increases/decreases.
Attention:
Note that stretching of the grid should be avoided in areas of the simulation domain where
the main combustion is happening. The flame model in FLACS has been validated for cubical
control volumes, thus the user should not stretch the grid in areas where accurate results are
required. It is however good practice to stretch the grid towards the boundaries, to concerve
simulation time and computer memory.
3.5.10 Information
The Information command displays status information about the defined grid, while the List
command lists the grid coordinates in the working direction.
3.5.11 List
The Information command displays status information about the defined grid, while the List
command lists the grid coordinates in the working direction.

58 CASD
3.5.12 Display
The Display command turns grid display off, displays the grid in the working direction only, or
displays the grid in all three directions.
3.5.13 Select
The selected region of grid planes is limited by two planes, the lower and upper limit. If only
one plane is selected, the upper and lower limit is the same grid plane. Grid planes are selected
using the following commands:
• Lower boundary
– Select the next grid plane: CTRL+RIGHT
– Select the previous grid plane: CTRL+LEFT
• Upper boundary
– Select the next grid plane: CTRL+UP
– Select the previous grid plane: CTRL+DOWN
3.5.14 Grid-related operations
3.5.15 Importing the grid from another job
Use the Import command in the File menu to import the grid from another job.
If you enter the grid file name in the command input field, the path must be encapsulated in
apostrophes, as described in section . If you select the command from the menu bar, or if no
name is specified in the command input field, the Import dialog box is displayed, allowing you
to specify the path and file name for a grid file. You will be asked to verify that the current grid
is overwritten by the grid from the specified file.
3.5.16 Saving the grid
The Save and Save As commands in the File menu saves the grid, together with the rest of the
job data. If the grid is changed, you will need to recalculate the porosities.
3.5.17 Grid-related utilities
FLACS is deleivered with a command line tool for creating an manipulating the grid. This tool
can be used to quickly edit or get information about the grid. Please see section gm for further
information.
3.5.18 Grid guidelines
The grid resolution should be chosen to obtain a simulation result within an acceptable time
frame. In most cases a reasonably good result can be obtained on a coarse grid within less than
one hour (in some cases 5 minutes), and high quality results can normally be generated in a few
hours (or at least over the night).

3.5 Grid menu 59
Never start a project with a calculation on a grid that will be running for days. If such long sim-
ulation times are necessary, always start simulating on a much coarser grid [even if this violates
guidelines] to check that the scenario and setup are OK.
The user should keep the position of the grid lines in mind while defining the geometry. The
geometry details such as walls and decks should be adjusted to the closest grid line when in-
putted. Thereby the user keeps track of the positioning instead of having the geometry moved in
an unwanted direction by the porosity calculation program.
In the grid embedding process, it is highly recommended to use Grid→Information in Casd to
check different aspects of the grid. Grid sensitivity tests are also recommended.
3.5.18.1 Gas explosion simulations
Attention:
The user should always apply cubical grid cells in the combustion region. Deviations from
this will give different flame propagation and pressures, and the validation work done is
no longer valid. Deviations of the order 10% in aspect ratio is OK, deviations by a factor
of 2 in aspect ratio is not OK. If one chooses not to follow this guideline, the results can be
somewhat improved by setting a fixed control volume size for the time stepping routine (see
section The SETUP namelist, example TIME_STEPPING=" STRICT:L_FIX=1.0" ).
Channels and confined vessels and rooms (filled with gas from wall to wall) must always be
resolved by a minimum of 5-6 grid cells in smallest direction if flame acceleration shall be modelled.
This also applies for pipes where flame acceleration along the pipe is of interest.
A pipe connection from one vessel to the next may have less grid cells across the diameter (but
preferably more than 1 CV) if only flame transport by pressure difference and not flame accelera-
tion along the pipe shall be modelled. Increase the inner diameter of angles and bends somewhat
when modelling pipes with cylinder minus primitives. Remember that one full grid cell is re-
quired inside the solid walls around " minus primitive holes" to ensure that the walls will not be
leaking.
Unconfined gas clouds as well as partially filled clouds should have a minimum of 13 grid cells
across the cloud if both sides are unconfined, and a minimum of 10 grid cells in directions where
cloud meets confinement on one side (example vertical direction for dense gas cloud in chemical
plant).
It is not recommended to use non-cubical grids for explosion simulations. As they are often used
for dispersion simulations, the dispersion simulation results should be dumped, thereafter the
rdfile utility program should be used to transfer the results from the dispersion grid to a grid
better suited for explosions, see example below:
> run9 rdfile rd111111.n001 rd222222.n001
Here 111111 is the dispersion calculation job number and 222222 is copy of the job, in which the
grid has been modified to follow explosion grid embedding guidelines. The grid of job 222222
must be completely inside the grid of 111111.
The grid can be stretched outside the combustion region in directions where pressure recordings
are not of interest. In directions where pressure wave propagation is of interest, one should not
stretch the grid because this will reduce the sharpness and quality of the pressures.
A proper distance to external boundaries is important. At least 5-10 grid cells from vent opening
to external boundary should be used in situations where the external explosion is not important
(small vent area or strong turbulence inside vessel).

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