2.0 GLOBAL CONTROL
2.1 Define a New Problem
DEFINE_PROBLEM
(new)
DEFINE_PROBLEM name = "<string>" , title =
"<string>" , etc....
The command serves as the
start of a new problem record. The
command also serves to define the control parameters associated with the
particular analysis to be performed.
Note Variable Name Type Description
Name string Name used to construct output results
files.
Name must be enclosed in quotation marks.
Title string Descriptive title (optional).
Title
must be enclosed in quotation marks.
Number_of_spatial_dimensions integer Number of
spatial dimensions 
1 and 
3
EXAMPLE
Define_problem /
name =
"problem_name" /
title = "problem_title"
2.2 Restart a Problem
DEFINE_PROBLEM (restart)
DEFINE_PROBLEM name = "<string>" , title =
"<string>" , etc....
The
command serves as the start of a new problem record. In the restart mode,
existing data may be modified and/or new data may be entered.
Name string [none] Name
used to construct output results files.
Name
must be enclosed in quotation marks.
Title string [last] Descriptive title (optional).
Title
must be enclosed in quotation marks.
Restart_name string [none] Name of problem_name defined by previous
run.
Name
must be enclosed in quotation marks.
Restart_at_time_step integer [0] Step number at which restart is to be
initiated.
EXAMPLE
Define_problem /
name =
"new_problem_name" /
title =
"new_problem_title" /
restart_name=
"old_problem_name" / # Problem
name to be restarted
restart_at_time_step = ns # Step number at which the restart is
to
be initiated.
2.3 Backup
a Problem
BACKUP
BACKUP Step_number = ns , etc....
The
command is used to backup current results in a restart file.
Step_number integer [0] Step number at which backups are to be
initiated
Backup_freq integer [0] Backup frequency 0
Backup_save integer [0] Number of backup files to be saved 1
=
0, save all backup files
Final_time list [off] Request a backup at end of run
on / off
EXAMPLE
Backup /
Step_number = ns / #
Backup starting at step ns
Backup_frequency = freq / # Backup every freq time step
Backup_save = nsave # Save nsave backup files
2.4 Time Sequencing
TIME_SEQUENCE
TIME_SEQUENCE number_of_time_steps = nts , etc...
Specify
global controls for time stepping and convergence.
•
Analysis Duration
Max_number_of_time_steps integer [NTS] Maximum number of time steps;
NTS_max
(1) Number_of_time_steps integer [0] Number of time steps NTS:
>
0 and NTS_max
Time_at_start real [0.0] Time at start of analysis 0
(1) Final_time real [*] Time at
which analysis is to end unless it
ends
earlier due to other criteria
(e.g.,
maximum number of time steps,
or
steady state convergence).
(2) Time_step real [1.0] Initial global
time step increment
size
Dt1 > 0.0
Time_unit list [*] Time unit
seconds
minutes
hours
days
months
years
•
Time Step Control
(3) Variable_time_step string [off] Variable time step option
on / off
(4) Convergence_index real [1.0] Convergence index
Load_time_function integer [0] Time step load-time function number 0
Multiplier_time_step real [1.0] Time step
multiplier
Iteration_threshold integer [0] Iteration
threshold below which time step
multiplier
is activated
(cont’d)
(cont’d)
Note Variable Name Type Default Description
Max_time_step real [Dt1] Maximum time step increment size
Min_time_step real [0.0] Minimum time step increment size 0.0
•
Recomputing Time Step
(4) Redo_on_divergence string [off] Redo time step on divergence
on / off
(5) Divergence_threshold real [0.0] Divergence threshold (
)
Max_number_of_redo integer [1] Maximum number of successive time
step
increment reductions if time step
is
repeated after failing to converge
( 1).
Redo_decrease_factor real [0.25] Factor used to reduce time step
increment
if time step is repeated after
failing
to converge. (> 0 and 1.0)
•
Steady-State Options
Exit_on_steady_state list [off] Select whether or not to end the run
on / off based
on steady state exit criteria.
Steady_state_freq integer [1] Frequency of steady-state checks 0
(e.g.,
every n time step)
EXAMPLE
Time_sequence /
Number_of_time_steps
= 10 / # number of time steps to
be performed
Time_step
= 1.E-2 # time
step Dt = 0.01
Notes/
(1) The number of time steps and/or the
final time are exit criteria to end the analysis. An analysis can end sooner due to other
criteria (e.g., an exit on steady-state criterion). However, an analysis ends after the maximum
number of time steps, or the final time if specified, whether or not a
steady-state solution has been reached.
(2) The time step must be sufficiently small
to accurately characterize the non-linear behavior, and to meet stability
requirements (if applicable).
(3) Variable time steps can be obtained by
using a corresponding load-time function, or a time step multiplier.
(4) A
convergence indicator is used to evaluate how well the time steps are
converging. This indicator is defined
as:
where 
= convergence
tolerance for the residual,
and 
(see Section 12.3 for
more details). If the convergence
indicator is less than zero the time step is diverging, whereas if it is
greater than zero and less than one, the time step is not fully converged.
(5) By
selecting the divergence_threshold the user may control when time steps not
fully converged are to be redone by decreasing the time step increment.
2.5 Echo
ECHO
ECHO <string>
The command is used to
display a message on the screen, or to send it to the log file, during a solver
input phase.
No name string Message
to be displayed can be any
number
of characters ( 80)
2.6 Print
PRINT
PRINT
The
command is used to request a comprehensive output in the result file of the
input data. The command may be inserted
at any place within the input file.
2.7 Noprint
NOPRINT
NOPRINT
The
command is used to suspend output of the input data (the default is
print). The command may be inserted at
any place within the input file.
2.8 Open
File
OPEN_FILE
OPEN_FILE file_name = "<string>"....
Open
the file named "<string>".
The file name must be enclosed in quotation marks. The command may be used during the input
phase to direct the solver to read an entire sequence of input commands in a
file distinct from the main input data file.
At the end, the file must be closed using the CLOSE_FILE command, to
redirect the solver toward the main input data file.
2.9 Close
File
CLOSE_FILE
CLOSE_FILE file_name =
"<string>"....
Close the file named
"<string>". The
file_name is optional.
2.10 Parameters
PARAMETERS
PARAMETERS a1 = etc...
The use of parameters can be used to
simplify the input data required to define a problem. Data may be specified as a single character
parameter (e.g., a, b through z), two character parameters (e.g., aa, ab, …), a
character and a numeral (e.g., a1 through a9), etc., up to three symbols. The only restrictions are that the data must
start with a character parameter and only contain character and numeral
symbols. All alphabetic input characters
are automatically converted to lower case, hence there are 35,594 unique
parameters permitted at any one time.
Parameters may have their values redefined as many times as needed by
using the PARAMETERS command.
EXAMPLE
Parameters /
a1
= 1.0, a2 = 2.0 /
b12
= 5, …
2.11 Run Solver
RUN_SOLVER
RUN_SOLVER mode = etc...
Direct the solver DYNAFLOW towards
an appropriate execution mode.
Note Variable Name Type Default Description
(1) Mode list [data_
check] Type of execution mode
data_check Data
check
execution Perform
analysis
Notes/
(1) The
Run_Solver command must be the last command of the problem record and is used
to direct the solver towards an appropriate execution mode. In the data_check mode, input data are read
in and printed out if requested, and storage requirements are indicated. This mode should be employed before making
expensive executions.
2.12 Stop
STOP
STOP
Exit
the input file, and ignore any subsequent commands. Alternatives are QUIT, EXIT, or STOP. The program also exits when it finds the end
of file mark in the input file.