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.
Wednesday, September 9, 2009
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.
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:
fds5_openmp.exe
fds5_openmp_mpi.exe
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!
As a test, I have posted to the Downloads page two executables:
fds5_openmp.exe
fds5_openmp_mpi.exe
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.
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
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
Subscribe to:
Posts (Atom)
