Fire Simulation for Engineers/FDS/General Configuration

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First, general configuration is performed.

The case receives a name via the HEAD namelist group, the simulation time is set via the TIME namelist group. Other miscellaneous parameters are prescribed via the MISC namelist group.

Naming the job, HEAD[edit]

The first thing to do when setting up an input file is to give the job a name. The name of the job is important because often a project involves numerous simulations in which case the names of the individual simulations can help organize the effort. The namelist group HEAD contains two parameters, as in this example:

&HEAD CHID='mycase', TITLE='This is a short description' /

CHID is a string of 30 characters or less used to name the output files created by FDS. No periods or spaces are allowed. TITLE is a string of 60 characters or less that describes the simulation. It is simply a descriptive text that is passed to various output files.

It is always convenient to exactly use the same string for the name of the input file and the CHID. For example, if you name mycase.fds the input file, then set CHID='mycase' in the HEAD namelist group.

Only one HEAD line can be entered in the input file. The following table summarizes some of the most used HEAD parameters.

Parameter Type Description Unit Default
CHID String Job identifier 'output'
TITLE String Short description of the job

Simulation time, TIME[edit]

TIME is the namelist group that define the time duration of the simulation. Usually, only the duration of the simulation is required on this line, via the parameter T_END. The default is 1 s.

For example, the following line will instruct FDS to run the simulation for 5400 s:

&TIME T_END=5400. /

If T_END is set to zero, only the set-up work is performed, allowing you to quickly check the geometry in Smokeview.

Only one TIME line can be entered in the input file. The following table summarizes some of the most used TIME parameters.

Parameter Type Description Unit Default
T_BEGIN Real Starting time for calculation s 0.
T_END Real Ending time for calculation s 1.

Miscellaneous, MISC[edit]

MISC is the namelist group of global miscellaneous input parameters. Many parameters for MISC exist, some of them are explained later in this manual.

For example:

&MISC SURF_DEFAULT='steel' /

establishes that all bounding surfaces are to be made of steel unless otherwise specified.

Only one MISC line can be entered in the input file. The following table summarizes some of the most used MISC parameters.

Parameter Type Description Unit Default
SURF_DEFAULT String Default boundary condition 'INERT'
TMPA Real Ambient temperature °C 20.
U0, V0, W0 Real Initial prevailing velocity field m/s 0.
GVEC(3) Real Gravity vector m/s2 0.,0.,-9.81
RESTART Logical Restart previous calculation .FALSE.