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ALOFT-FT Frequently Asked Questions

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General

What operating systems does ALOFT-FT support?

ALOFT-FT installs and runs with Windows 98/ME/NT4/2000/XP®. The graphics may not work on some Windows 95 computers. The program is a 32 bit application and will NOT run under Window 3.X with win32. There are no plans to support Windows 3.X, Macintosh® or UNIX at this time.

What is the difference between ALOFT, ALOFT-FT, ALOFT-CT and LES?

ALOFT is the general name for the family of programs which include ALOFT-FT™ (flat terrain) and ALOFT-CT™ (complex terrain). Presently only ALOFT-FT is available in a personal computer version. The ALOFT models are based on the large eddy simulation (LES) technique. This technique can also be applied to indoor fires. To avoid confusion, the LES model for outdoor fires was renamed ALOFT.

How do I remove the program from my computer?

You should use the Add/Remove Programs feature in the Control Panel. Deleting the folder with the program will not remove files in the system directory and update the registry. If the folder is with the program is deleted, it will remove the information required for the Add/Remove Programs feature to function properly.

Can I modify the program myself?

The practical answer is no, however, we are interested in your suggestions. Many of the features in the program were suggested by users. The program is rather large and is written in FORTRAN and Visual Basic. The program uses a number of third party controls or routines which can be used in the run-time mode without royalties. To use these routines in the development mode, the user would have to own copies of that software. NIST has filed a trademark application for the name ALOFT™ and variations such as ALOFT-FT™. The use of these names with a modified program would be considered a violation of the trademark. The program can be freely used and distributed since it is in the public domain and not subject to U.S. Copyright.

Can I run the computational portion of the program without the user interface?

While the program could be set up this way we have chosen not to. The user interface is a convenient way to enter the data and provides substantial error checking.

Can I edit the data files with a text editor such as Notepad?

It is possible to edit the data files with a text editor but it is not recommended. If changes are made to a data file that do not conform to the proper data file format, the program may be unable to properly interpret the data. Directly editing a data will not allow the user to bypass the limits set in the user interface. The data is always rechecked before running the computation.

How can I speed up the program?

There are two ways to speed up the program. The most obvious and costly is to use the fastest computer possible. The most important is to make a prudent selection for the downwind distance. ALOFT-FT computes the solution starting at the fire and works downwind. Thus, the greater the downwind distance, the greater the computation time. The computation time is not directly proportional to downwind distance since the program uses variable time stepping and some functions are independent of downwind distance.

Can I get a printed copy of the User Guide?

The user guide is included with the program in the Windows help file format. This saves publication cost and ensures the guide is always up to date. A windows help file cannot be viewed properly with a word processor. The help routine can be used to print some or all of the guide.

Where can I find the equations used in ALOFT-FT?

The principal technical reference for ALOFT-FT is available for download.

NISTIR 5958 Smoke Plume Trajectory From In Situ Burning of Crude Oil in Alaska: Field Experiments and Modeling of Complex Terrain. McGrattan, K. B.; Baum, H. R.; Walton, W. D.; Trelles, J. J.

NISTIR 5958 includes the equations and comparison of model results with experiments for ALOFT-FT and ALOFT-CT. This is a comprehensive reference but it is a large file.

See ALOFT-FT Download for information on downloading this document.

Additional ALOFT references may be found in BFRL Publications Online and searching under the author name McGrattan.

What are the limitations for using ALOFT-FT?

  • Downwind Distance 0.5 km to 20 km, 0.3 mi to 12.4 mi
  • Distance Over Water greater than 0 km to 20 km, 0.3 mi to 12.4 mi
  • Heat Release Rate per Unit Area greater than 0 MW/m2 to 5 MW/m2
  • Burning Rate per Unit Area greater than 0 kg/s-m2 to 1 kg/s-m2
  • Fire Area 25 m2 to 1000 m2, 269 ft2 to 10763 ft2
  • Wind Speed 2 m/s to 15 m/s, 4.5 mi/hr to 33.6 mi/hr, 3.9 kn to 29.2 kn
  • Sigma Theta Over Land 2.5 degrees to 25 degrees
  • Sigma Phi Over Land 2 degrees to 17 degrees
  • Sigma Theta Over Water 1 degrees to 15 degrees
  • Sigma Phi Over Water 1 degrees to 12 degrees
  • Surface Temperature -60 degrees C to 100 degrees C, -76 degrees F to 212 degrees F
  • Lapse Rate greater than -9.5 degrees C/km, -5.2 degrees F/1000 ft
See on-line help for detailed information.


Display

Can I display the ALOFT 3-D graphics found on the WEB page?

The 3-D images were produced on a graphics workstation from the standard ALOFT-FT and ALOFT-CT output files using commercial scientific visualization software. Visualization software is available for personal computers but it is usually expensive. The ALOFT-FT output file format is described in the help file.

Why are the program windows small on my large screen monitor?

The ALOFT-FT display screens are sized to fit screens with a resolution of 640 by 480 pixels or greater. ALOFT-FT does not automatically adjust the output screens to the system screen resolution.

The text on my summary graph overlaps.

One user has reported the text on the summary graph overlaps both on the screen and in the printouts. We are looking into this problem which is probably related to the fonts installed on that computer.

Why are unit names spelled out on the graph screens and in the online help?

The use of special characters is more difficult in programs than it is in a word processor or web page. We are investigating ways to address this problem.

 

Database

I can’t find the fuel I’m looking for in the database.

Some of the fuel parameters may be available in the literature. It is rather costly to develop a complete set of parameters for a fuel. We have no plans to add additional fuels at this time.

I deleted a fuel I need from the default database. Can I reload it without reloading the entire program?

There are two possible fixes for this. The ALOFT-FT install routine loads two copies of the same database onto your computer. One is called FUELS.MDB and the other FUEL.MDB. By default the program will use FUELS.MDB but you can use the LOAD DATABASE option to load a different database. If you have created a data file which contains the deleted fuel it can be added to the database by opening the data file. The program will search the database for the fuel in the data file and, if it is not found, allow you to add it to the database.

Can I copy fuels from one database to another?

Not directly, however, fuels can be copied one at a time using the program. To do this create a data file which contains the fuel you which to copy. Make sure a fuel with the same name does not already exist in the database you are planning to copy to. Under the FILES menu select OPEN DATABASE and select the target database. The program will check the new database to see if the fuel exists. If it does not exist, the program will allow you to add the fuel to the database, thus copying a fuel from one database to another.