Tuesday, December 8, 2009

Maintenance Release of FDS 5.4.3

There is a new maintenance release of FDS/SMV on


Please note that for those of you who are not using the 32 bit Windows versions of FDS, there might have been a change to the name of the executable. After downloading the new version, go to the directory where the program was installed and check that there are no older versions present (or rename them if you want to keep them). When in doubt, simply type the name of the executable at the command line and see that the release number is the most current.

Wednesday, November 18, 2009

The FDS/Smokeview Issue Tracker

Over the past year, I have noticed that the FDS/SMV Discussion Group has changed its focus from general questions, comments and discussion to bug reporting. This is just a quick note to remind everyone that the best way to report a bug in FDS or Smokeview is via the Issue Tracker


and not the Discussion Group. There are several advantages to using the Issue Tracker:

1. It is easier to upload files.
2. The case is assigned to one person and a record of progress is maintained.
3. The rest of the community need not follow the specific details.
4. It provides a good way to collaborate because there is a running record of who has done what and when.

The most important reason for using the Issue Tracker is that it is vital part of our verification process. If you report a bug, and we fix it, there is a record of what was done and why. There is also a way for you to check that the fix worked, and for us to close the case. When we fix a reported bug, the case is marked "Fixed" and the person reporting the bug ought to get an email notice to this effect. It is very important that the person reporting the bug then go and try the latest version to see if the bug has truly been fixed. It is not enough for the case to be marked "Fixed" by us -- it must be "Verified" by you.

So please, those of you who have reported bugs to the Issue Tracker in the past few months, if your case is still only marked "Fixed", could you let us know if the latest version of FDS or Smokeview really fixed the problem. Then we can close the case.


Tuesday, October 20, 2009

Appeal for FDS/Smokeview References

Last summer, I broadcast a request to the FDS/SMV user community to send us references to journal articles that involved FDS verification or validation. We have literature survey sections in both the Verification and Validation volumes of the FDS Technical Reference Guide


that we would like to keep up to date.

Unfortunately, I received only 5 references in over a year, and 3 were from the same person! I'd like to repeat my appeal. Please understand that it is very important that we document FDS V&V work, both the work that we do ourselves and the work done by others. An added benefit is that these papers can help those who are just starting to use FDS understand capabilities and limitations.

For those who have published articles that involve FDS V&V, could you please do the following:

1. Scan the literature survey chapters of either the Verification or Validation Guide to see if your paper is referenced. If it is, please check the reference for accuracy. If it is not, then

2. Send us the reference. To save us some time, it would be very useful to send the reference in this form:

author = {Hostikka, S. and McGrattan, K.B.},
title = {{Numerical modeling of radiative heat ...}},
journal = {Fire Safety Journal},
year = {2006},
volume = {41},
pages = {76-86}}

We use LaTeX for our documents, and this is the standard format of a reference in the bibliographic database. Even if you do not know LaTeX, getting the information in something close to this format would be a big help.

3. Send an electronic copy of the article, if possible. We cannot post the article because of copyright issues, but it is nice to have the document on file. Plus, it will enable us to write a few sentences in the V&V Guides describing the work. If you could summarize the work in a few sentences, that would be a great help, too. We do not need too much detail. We only want to provide enough information so that the readers can find and read the paper themselves.

For articles that you think appropriate for the FDS Verification Guide, send the information to


For Validation work:


And let's not forget that Smokeview is subject to V&V too:



Release of FDS 5.4.2

A new maintenance release of FDS, version 5.4.2, is available at


This release contains a number of bug fixes related to experimental routines known collectively as "FDS 6". These changes should not affect the current FDS 5 default functionality. We are gradually working in these improvements to FDS while continuing to maintain the current capabilities. This should make the transition to the new routines smoother once they have been thoroughly shaken down. Many thanks to those of you who have been playing with the new routines. It is only through this process that we can work out the kinks.

Wednesday, October 7, 2009

NIST Building and Fire Research Division Postdoctoral Opportunities

BFRL postdoctoral positions are currently available for Ph.D. engineers, mathematicians, and physical scientists. Proposals are solicited on the following topics: Fire Metrology, Combustion Fundamentals, Fire Simulations, Flammability and Material Behavior in Fire, Fires at the Wildland-urban Interface (WUI).

There is a PDF flyer with more information about the positions available here:

For information about working in the Building and Fire Research Laboratory see the “careers” page: http://www.bfrl.nist.gov/careers/

Persons interested in any of these opportunities or with career questions may contact or submit a CV/Resume to bfrlcareers@nist.gov.

Building and Fire Research Laboratory
100 Bureau Drive, Stop 8600
Gaithersburg, MD 20899-8600
(301) 975-5900, TTY (301)975-8295
FAX (301) 975-4032

Thursday, October 1, 2009

Computational Wind Engineering 2010

Professor Robert Meroney of Colorado State University asked us if we would post the following information:

We are setting aside a special session during the Fifth International Symposium on Computational Wind Engineering next spring in Raleigh, N.C., May 23-27, 2010 (Web site is http://www.cwe2010.org/index.html ). This symposium draws participants from architects, engineers, city planners, environmental responders, etc. Unfortunately, we have not had much response from the many fire modelers I know are active. Although the official deadline for abstract submission (1 page) is October 1, 2009, we intend to extend the deadline a couple weeks further into October. Below is a description of the special session:

Fire modeling

Although fire modeling in general can include conceptual, physical, or analytical models, the computational wind engineering focus is on how numerical methods (CFD) can be used to interpret how forest, brush, and/or building fires interact with local meteorology. Examples are the influence of local wind and atmospheric conditions on the spread and intensity in structure fires, wild land/urban interface fires, fires in urban street canyons, and forest/brush fires aggravated by local environments such as vegetation, canyons, or topographical channeling.

Robert N. Meroney, PhD, PE
Colorado Professor Emeritus
Civil and Environmental Engineering
Colorado State University

Tuesday, September 22, 2009

Modified FDS 6 Options

For anyone testing FDS6=T on the MISC line, please be aware that with the latest SVN (4801) there have been some noteworthy modifications. Generally speaking, these modifications are the result of experience gained by solving issues presented by our user community and we would like to thank those who have contributed to this effort. It is simply not possible for the developers to test every possible scenario the user may encounter: your feedback is invaluable.

The original list of FDS6 options can be found here:

This list has been modified as follows:

1. CHECK_KINETIC_ENERGY=F is the new default. This is a rather inconsequential change, but as we get further into the development cycle timing becomes a more important concern and so removing this flag as a default provides a closer comparison with FDS 5. If the user wishes to output QUANTITY='TURBULENCE_RESOLUTION' then they need to set CHECK_KINETIC_ENERGY=T on MISC.

2. PROJECTION=T (on MISC) is a new option in FDS6. With this option the time integration scheme is a true projection method. Because of the current structure of FDS 5 this option uses more flops, but in my experience this is not noticeable. So, what is a true projection method as opposed to the usual scheme in FDS 5? In FDS 5 the assumption is made that the pressure field obtained from the Poisson solve will force the velocity to exactly match the velocity divergence computed from the time derivative of the equation of state. Because we use a direct Poisson solver at the end of a time step the actual discrete velocity divergence is very close to an exact match of the desired velocity divergence from the equation of state. BUT, on the next time step whatever error (however small) that we incurred on the previous time step is still present. For very refined and long-time calculations there is the possibility that this error could become significant, potentially even causing an instability. Put simply, a true projection method does not have this deficiency. On every time step the velocity field is projected to match the desired divergence and the error from the previous projection is erased. Provided this method can be made as efficient as the FDS 5 method -- and it can with the proper code structure -- the true projection is clearly the more desirable approach.

3. For DNS=T we now set FLUX_LIMITER=4. FL=4 invokes the Charmers limiter which is convergent whereas FL=2 invokes Superbee which does a better job at retaining shocks in the scalar data but is not convergent. We hope to eventually have a scheme that smoothly transitions from one method to the other (FL=2 to FL=4) as the grid is refined (i.e. as we converge from LES to DNS).

In addition to the modifications listed above, a significant improvement has been made to the stability check (i.e. the time step calculation) used in FDS 6. In short, the previous method was overly restrictive and was adding unnecessary computational expense to FDS 6 calculations. What we find now is that the cost of the velocity calculations in FDS 6 are roughly 16% more than FDS 5 due to the calculation of the dynamic Smagorinsky constant. But, we also find that the mass transport routines are half the cost of FDS 5. The overall cost difference is problem dependent but we feel we are slowly trimming the fat from FDS 6.

Please keep your observations coming (with the latest SVN, of course :))!

Friday, September 18, 2009

FDS Verification and Validation

A few years ago, Prof Jose Torero of the University of Edinburgh remarked during a presentation that for any given quantity that you might want to predict with a fire model, you can find 2 or 3 papers in the literature that report that FDS works well, and 2 or 3 that report that it does not work well. Putting aside for the moment what is meant by "works well," the point Jose was trying to make is that it is very difficult for practicing engineers to know when to trust or not trust model predictions. The complementary processes of Verification and Validation are intended as checks of the mathematical algorithm and physical submodels, respectively, and there has been a considerable amount of work to V&V FDS over the past decade. Yet, the problem Jose alludes to remains.

When FDS was first released, we had in mind the idea that V&V would be performed by students and engineers using the model for research or commercial applications, and the results would be published in the fire literature. This did indeed happen, and there are numerous papers, reports, and theses spread across the various journals and websites. However, several years ago as we were working on a V&V study with the US Nuclear Regulatory Commission, it became apparent that we could not just depend on the fire literature as a repository of FDS V&V work. There were several reasons:
  1. V&V, especially Validation work, cannot be easily crammed into a short journal article.
  2. Results of older versions of the model lose their validity after a few years.
  3. Often the experimental conditions and uncertainties are unknown.
  4. Often the work is performed by students who are just learning how to use the model.
  5. There are too many different ways of quantifying accuracy, which gets back to the question above as to what "works well" means.
  6. Cases have to be re-run with each new release, and we cannot expect journals to keep publishing the same old stuff.

For these reasons, we decided to maintain two manuals, Volumes 2 and 3 of the FDS Technical Reference Guide, called the FDS Verification and Validation Guides, respectively. In these, we have compiled existing V&V work and continually add case studies to demonstrate mathematical accuracy and physical fidelity. The Validation Guide


now has hundreds of experiments and thousands of individual point to point comparisons for a wide variety of output quantities. The Verification Guide


is more recent, but it is growing.

Everyone who is using FDS ought to familiarize themselves to some extent with these Guides. They are not the sort of thing you sit down and read, however. Rather, they are reference documents that you should refer to whenever the question arises, "Can FDS do that?"

We would like to especially encourage students who are interested in working with FDS to look through these Guides. More than anything else, they indicate subjects of current interest, especially areas that we are working to improve. In addition to consulting these Guides, we encourage you to contact us via the Discussion Group (or off-line if you like) and indicate which areas you might want to work in. Using specific examples directly out of the V&V Guides is a great way to start a collaboration because we are familiar with the cases and either the analytical or experimental technique. It is far more difficult for us to work with you when all we see are a few comparisons of FDS with experiments we are not familiar with. The value of working with such a large amount of test data is that anomolies in one or two experiments become outliers when compared to hundreds of other measurements.

If you have a verification case or an experimental dataset(s) that you would like to contribute, it would be very helpful if the data and FDS input files could be prepared in a way that is similar to the cases already in the repository. It takes a significant amount of time to boil down megabytes of test data into a form that can be easily plotted and compared to the model. We do not have enough time to take a test report, set up the input files, work the experimental data into a useable form, run the cases, prepare the output graphs, and document the process for each and every experimental test series. If you have already done this, it takes much less time to re-organize the material into a form that we can easily work into one of the Guides. But, please contact us early in the process. There are plenty of useful techniques we have developed for doing V&V, and it these are adopted early, there is a much greater likelihood that the work will make a significant contribution to the whole project.

Wednesday, September 9, 2009

FDS 5.4 Release -- A Few Installation Issues

Thanks to all of you who have given feedback on the new release of FDS, version 5.4. We're currently fixing a few problems related to the Mac installation and the OpenMP test for Windows. We'll post an update when these are ready for use.

Also, note that these blog posts automatically get posted to the FDS-SMV Discussion Group. So please respond with comments in the Discussion Group so that we can maintain a consistent thread.

Tuesday, September 8, 2009

Pyrolysis Model in FDS

In the next few weeks we plan to write a few articles to alert you to some changes made in FDS 5.4. This article focuses on the solid phase pyrolysis model; that is, where you specify a reaction or reactions that the solid undergoes in releasing fuel gases. There is still confusion among users as to the various ways that you can describe a fire. Most simply specify a heat release rate per unit area (HRRPUA). In that case, there is no need to provide more details about the solid phase reaction. HRRPUA is equivalent to a gas burner that you control via RAMPs or similar parameters.

However, if you specify material (MATL) properties, including kinetic parameters, to describe one or more reactions that occur as your solid heats up, be aware that the definition of the parameter REFERENCE_TEMPERATURE has changed in 5.4. In previous versions of FDS, this parameter, along with REFERENCE_RATE, was used to calculate the Arrhenius parameters A and E in the reaction rate expression. These parameters are typically found via thermo-gravimetric analysis (TGA) or similar small-scale measurement techniques. Since these measurements are most often unavailable for a particular material of interest, FDS provides a way, via these "reference" values, of estimating the kinetic parameters. You have also probably seen discussion of genetic algorithms that also are intended to estimate various kinetic parameters when only a partial number are measured directly.

The change made in FDS 5.4 to the definition of REFERENCE_TEMPERATURE was intended to make the FDS pyrolysis model more consistent with current trends in materials testing and analysis. For a good introduction, read Jose Torero's chapter, "Flaming Ignition of Solid Fuels," in the Fourth Edition of the SFPE Handbook. Then read the FDS User's Guide section entitled, "Solid Fuels that do NOT Burn at a Specified Rate." All of this development is focused on the long-term goal of standardizing the process of obtaining material property data. A necessary first step is to understand the meaning of typical TGA results (a good example can be found in Torero's chapter). Then we need to translate this information into FDS inputs.

We'd like to continue the dialog on pyrolysis modeling that started last year, but has recently stalled a bit. We are starting to notice yet again that many users are simply cutting and pasting lines of input from the User's Guide and sample cases without really understanding their meaning. We are developing a suite of verification cases that can be used to check the basic kinetic parameters (a simulated TGA experiment), as well as cases to assess the overall solid phase model (a simulated cone calorimeter measurement). Nick Dembsey, Marc Janssens and Morgan Hurley are continuing their multi-year effort to develop a standard guide for obtaining material properties. Our work in FDS will hopefully move us closer to the goal.

So for those of you with an interest in this area, it would be very useful to get your feedback. I will post this blog to the Discussion Group so that it will appear near the top of the list of issues.

Friday, September 4, 2009

FDS and OpenMP

Christian Rogsch of the University of Wuppertal has implemented OpenMP directives that enable FDS to make use of multiple processors on a single computer. This is a second option for running FDS in parallel. In fact, although it still needs a bit of testing, OpenMP and MPI should work together. OpenMP (Open Multi-Processing) will run a single mesh FDS job faster by making use of all available processors on a single computer. MPI (Message Passing Interface) requires that you break up the single mesh into multiple meshes, each of which runs on a separate computer. Ideally, we should be able to break up a case over multiple meshes on multiple computers using MPI, and allow OpenMP to run the individual mesh calculations faster.

As a test, I have posted to the Downloads page two executables:


These are for 32 bit Windows machines. If this test is successful, we will compile and release executables for other platforms as well. Note that there is currently no guidance in the User's Guide about OpenMP. These executables should work just like fds5.exe and fds5_mpi.exe. That is, there should be nothing you need to install, and you should not need extra libraries. At least, that is what we hope and why we need to test these before doing a more general release. What you should notice is that when you run fds5_openmp.exe on a job, all of your available processors or cores should work on the case. You can check your system performance to make sure.

Please let us know if these executables work for you, or more importantly if they don't. Of course, you need to have a computer, or computers, with multiple processors. At the start of the run, FDS should tell you how many processors (or "threads") it thinks it has access to.

Good luck and thanks again to Christian for all his efforts!

Wednesday, September 2, 2009

Release of FDS-SMV 5.4

We have posted a new "minor" release of FDS and Smokeview on the Downloads page. You can navigate there from the FDS/SMV homepage fire.nist.gov/fds. Remember that a "minor" release means that some features of FDS have changed, in particular the velocity boundary conditions and certain aspects of the solid phase pyrolysis model. The new FDS User's Guide, which comes with the Download, has more details.

Note that we have changed the installation process of FDS/Smokeview for Windows users. First, the new default installation folder is

C:\Program Files\FDS\FDS5

The purpose of this change is to enable us to start development of FDS 6 without having to overwrite current files. The other change in the installation process is that we are only using the program WinZip for the installation. WinZip has a nice feature which allows you to download files and unzip them into a given folder. It makes it easy for us to "bundle" the files needed for installation. A problem with past releases has been that we would release a "bundle" for every minor version of FDS, but then released separate executables for each maintenance release. We have found that many used the bundles only but did not update the maintenance releases. From now on, each new maintenance release will have all the necessary files for a full installation.

Note that as part of the new installation, there is a short program that will change the "path" variables to point at the new installation folder. Once you install the new version and restart your computer, the commands "fds5" and "smokeview" will now point to the new version, not the old. You can go back to an older version by just moving the appropriate executable from the old folder to the new. Whenever you type a command at the prompt, Windows searches through the path folders until it either finds or does not find the command. If something does not work properly, check your "Environment Variables", which can be found under "System Properties" --> "Advanced" on most Windows machines. I have found it useful to look at these "path" variables from time to time because many common software problems can be traced to bad path variables.

In the coming weeks, we will post additional information about the new release and features. For now, it would be useful to us if you could try installing the new version and reporting back to us via the Discussion Group any problems you encounter. The same is true for Mac and Linux users. The installation for these platforms is still basically a zip or "tar" file, but the new executables may or may not work properly because we have upgraded to Version 11 of the Intel Fortran compilers.

Tuesday, May 26, 2009

New FDS-SMV User Community Map Available

I have always wondered how many people are using FDS and Smokeview, and where in the world are they?  Maybe you wonder the same thing?  Well, to help answer this question, I have started a Google Map that can be edited by anyone, so that members of the community can add a place marker for where in the world they use FDS and Smokeview.

Link to FDS-SMV User Community Map

There is no requirement to do this, but I hope that everyone will take a few minutes to visit the map, click the edit button to the left of the map, and add a marker for where they are using the software.  In the marker title and description, feel free to include as much information as you like.  Some suggestions would be your Name, Google Group username, email address, company name, how or why you use FDS-SMV, links to papers written about your use, etc.

Some interesting features of using the map, is you can view the markers and user contributed information on Google Earth, and/or you can subscribe to the RSS feed for the map, so that you can monitor new additions to the map as they happen.

Please feel free to share this map with others who you know use FDS-SMV so that they can be added too.  I will be watching the feed and look forward to seeing your markers.

-Bryan Klein

Monday, April 20, 2009

Fire Modeling Workshop Live Blog and Video Feed.

During the Fire Modeling Workshop at the NIST Annual Fire Conference, we will be live streaming the event. You can find the page for the stream on the FDS-SMV site: http://fire.nist.gov/fds/FireModelingWS2009.html

Before the event, feel free to respond to the information form at the bottom of the live stream page.

There are two components to the stream, a live blogging system and a live video stream. Both components will be integrated and accessible through the same page. The live blog will allow participants, not at the event in person, to post comments or questions to be asked during the workshop, a moderator will be watching the comments stream and selecting some to be asked during the Q&A portion. Attendees who are there in person with a laptop, can also connect to the NIST visitor wireless network and comment and ask questions through the same system.

The video and live blog will be archived and made available on demand after the conference for review by those who cannot participate in real time. Information about how to access the archives will be made available after the event on the same page linked to above. We will then create new threads in the FDS-SMV discussion group to discuss issues raised during the workshop.

We hope that these services lower barriers to the information presented during the conference, and at the same time increases the ability for the Fire Modeling community to participate in the event, even if they cannot attend in person.

Before the event, you can test your computer's connection to the services at a demo site.


Friday, April 10, 2009

NIST Annual Fire Conference

This is just a reminder that the NIST Annual Fire Conference is taking place April 28-30, 2009, in Gaithersburg, Maryland. The workshop agendas have been posted to the web site:


The last day for registration is Wednesday, April 22. There is no fee, but all who attend must register to enter the NIST grounds.

The workshop on fire modeling is Wednesday, April 29.

Friday, April 3, 2009

FDS-SMV Project 'Public Domain' License.

Google Code Project Hosting, which we use for our development process, updated their licensing options to include 'Public Domain' as a valid type. This is applicable for US Federal Government Agencies like NIST who by US Copyright law, are required to release their works as Public Domain. http://en.wikipedia.org/wiki/Public_domain

Chapter 1 of Title 17 of the United States Code states:

§ 105. Subject matter of copyright: United States Government works37
Copyright protection under this title is not available for any work of the United States Government, but the United States Government is not precluded from receiving and holding copyrights transferred to it by assignment, bequest, or otherwise.

When we first setup the fds-smv project we had to select a license option to get the project in the system. At the time the MIT license was the most liberal from those we had to select from. But, still even though we picked MIT for Google Code Hosting requirements, we were careful to clearly state where relevant that everything we are creating and releasing is Public Domain according to US Copyright Law. It took some time in limbo, after some online and offline discussions with the Google Code Hosting Developers, but eventually it all worked out. This additional license option is great news for US Government Open Source Software (OSS) developers, as now we can select the correct option and use these tools without any confusion as to the type of license applied to the work product.


Tuesday, March 31, 2009

FDS Configuration Management Plan

Some of you who participate in the FDS/SMV Discussion Group might have noticed an interesting thread lately that concerned the process that we use to update versions of FDS and Smokeview:


In the US and worldwide, there are various standards used to evaluate the process by which engineering software is developed and maintained. For example, NQA-1 and ISO 9001 come to mind. Just do a search on these terms for more information.

The "process" that I speak of goes beyond the technical description of the model algorithm and the Verification and Validation (V&V) work that is documented in the FDS Technical Reference Guide, volumes 1, 2 and 3. It involves everything we do on a daily basis to develop and maintain the model and the software -- this blog, the Discussion Group, the Issue Tracker, the repository, and so on. Because questions like those in the discussion thread above need to be answered, we have issued volume 4 of the FDS Technical Reference Guide:


"Configuration Management" is the term that is commonly used to describe the process of developing and maintaining software.

For those of you who have an interest in this aspect of our work, please let us know what we can add to this Guide to make it easier for you to use. If there is information missing, let us know and we'll add it. We'd prefer that this Guide not get needlessly filled with useless information and excessively bureaucratic language. It should be a straight-forward description of what we do to maintain FDS and Smokeview.

Also, if you or your organization have put FDS/SMV through some sort of "process evaluation" and you are at liberty to share your experience, please do. One of the most important aspects of these process evaluations is peer review, and that term is used in the broadest sense. For example, our experience with the US Nuclear Regulatory Commission is a good example of peer review in that this organization has evaluated our models for certain types of applications. It is a bit tedious to do one of these evaluations starting from scratch. It would be far better to refer to what others have done already.

Monday, March 30, 2009

FDS email list

Be advised that this email list is to be discontinued. If you want to
continue to get postings concerning FDS or Smokeview, subscribe to our blog


Kevin McGrattan
National Institute of Standards and Technology
100 Bureau Drive, Mail Stop 8663
Gaithersburg MD 20899
Phone: 301 975 2712
Fax: 301 975 4052

Friday, February 6, 2009

FDS 5.3 Release

FDS Version 5.3.0 is now available for downloading. Follow the link from:


This is considered a "minor" release of FDS. Details of new features, and an explanation of what we mean by "minor" release, can be found at the following page:


A note about this blog -- we have maintained an FDS/Smokeview blog ("web log") for several years, but until now we have not had much traffic on it. No doubt this is because there are various other means of communicating information about FDS and Smokeview, and there is only so much information that any one person can handle. However, our original e-mailing list has become a bit outdated, and it's time to take advantage of the new tools that are being developed to circulate information. There are a variety of ways that you can now monitor the activity of FDS/Smokeview development, including periodic blog posts.

Another motivation for making greater use of the blog is that occasionally we find a topic or posting in the Discussion Group


that deserves greater attention. We may invite, from time to time, the author or authors of a particular post or discussion thread to write a blog post that will be broadcast to the entire user community. The blog will contain more general discussion, rather than details of a particular feature of FDS or Smokeview that you would normally find in the Discussion Group or Issue Tracker.

But do not fear -- you will not be bombarded by the blog posts on a daily basis. They will come periodically if you have signed up for email notification or an RSS feed.