Last change: $Id: chapter_4.0.html 108 2007-08-24 15:10:38Z fricke $
Before carrying out a model
run, the user
has to /determine/ a data set - the model parameters - e.g. how
many grid points are to be used, how large the horizontal and
vertical grid spacing should be, which kind of boundary conditions are
to be used for the individual variables, which numerical schemes
implemented in the model are to be used, how long the simulated time
should be, at which times and points plot output are supposed to be
made, etc.
These data are
assigned with the help of
so-called “NAMELIST-driven input” (FORTRAN -
NAMELIST –
input). The chosen values of the model parameters are
written
into an ASCII file with fixed format, which is expected by the model as
an input
file under the local name PARIN.
On this file the parameters are represented by their variable names
they have in the model. These parameters can be assigned one or more
values, depending on the type and size the variable has. The following
example shows the format of the file
PARIN:
&inipar
nx
= 79, ny = 79, nz = 40,
dx = 50.0, dy = 50.0, dz =
50.0,
initializing_actions =
"set_1d-model_profiles",
prandtl_layer = .TRUE.,/
&d3par end_time = 9000.0, section_xy = 1, 10, 20,/
&packagename var1 = .TRUE. /
&userpar
abcd = 1234,0,/
The parameters
are separated into four
different groups which all start with the so-called NAMELIST group
names.
These are &inipar,
&d3par
and &packagename
as well as &userpar.
In each case a
group is terminated with one backslash ("/"). Between the beginning of
the line and the group name at least one blank has to be typed. Between
the
group names and the "/", the
values are assigned to the variables. The example shows that in
principle all FORTRAN data types are allowed. For more details
concerning the NAMELIST syntax, refer to
appropriate FORTRAN manuals.
Parameters belonging to the group inipar are first read by PALM. These are the initialization parameters. Second, the so-called run parameters belonging to the group d3par are read in, then the parameters for steering the optional software packages (group packagename, the string "packagename" must be replaced by the NAMELIST group name of the respective package) as well as user-defined parameters (group userpar). The four groups must be given in this order, the last groups, packagename and userpar, may be omitted. If several software packages are selected (see chapter 3.7), further NAMELIST groups may be inserted before the group userpar.
The initialization, run and package parameters differ as follows:
The initialization
parameters are steering the basic settings of the model run.
They
define e.g. the number of the grid points, the numerical schemes to be
used, initial and boundary conditions to be applied, how the
three-dimensional fields are initialized at the beginning of a model
run (constant value profiles or 1D-model-pre-run, the initial
temperature profile etc.). These parameters apply to the total model
run and thus can not be changed with restart runs! If one tries to
change these values within the NAMELIST input file of a restart run,
then these changes are ignored (sole exception is the parameter initializing_actions, which
must be given the
value read_restart_data for restart
runs).
The run
parameters are generally steering actions to be carried out
during
a model run. One can select for example, at which times plot output
should happen and which variables are to be written. Additionally one
can (and must) specify the time to be simulated. Run parameters only
apply to the actual run (job) and with each restart run other values
may be declared (if runs are restarted automatically, parameters will
usually keep their values, provided that the NAMELIST input file was
not changed by the user in the meantime).
Package parameters behave like run parameters. Package parameters determine the behavior of the additional (not user-defined) software packages .
The user-defined parameters are assigned by the user within the NAMELIST group name &userpar (see chapter 3.5.2). They steer actions programmed by the user. By default, this group has only one parameter (region). If the user don't want to assign any values to the user-defined parameters, the group userpar may be omitted. The group name &userpar can be changed by the user in the user-defined code. In addition to this, further NAMELIST groups may also be declared (all within routine user_parin in file user_interface.f90). Chapter 4.4.1 shows a simple but complete example of the input file PARIN. This example file can be used together with the configuration file (described in chapter 3.2) for the execution of a model test run.
PALM assigns default
values to nearly all parameters. They become effective
if no other assignments are given in the parameter file. These
default values as well as the parameter name, type and its
explanation are described in the lists of the following subsections.
Last change:
$Id: chapter_4.0.html 108 2007-08-24 15:10:38Z fricke $