# Documentation du code de simulation numérique SUNFLUIDH

## Web LIMSI

sunfluidh:tuto1_simulationcontrol

### Simulation control data set

We here resort to a specific namelist named “Simulation_Management. It is also used in the next section “Data acquisition”. We specify here some parameters in order to define the numerical time step as well as stop criteria and recording rates related to backup and check files. Two examples are given. The first one corresponds to a simulation starting at t= 0 with a variable time step.

 &Simulation_Management Restart_Parameter= 0                             ,!--- Option value for starting the simulation from t=0.
Steady_Flow_Stopping_Criterion_Enabled = .false. ,!--- Stop criterion for steady flows. When it is enabled, residues between two successive flow fields are computed
Steady_Flow_Stopping_Criterion = 1.D-20          ,!--- convergence tolerance threshold for a steady flow solution (it works only when the previous parameter is enabled)
Temporal_Iterations_Number = 10                  ,!--- maximum value of time iterations before stopping the computation
Final_Time = 3.D+01                              ,!--- Maximum value of time before stopping the computation
TimeStep_Type = 1 ,                              ,!--- Option value for specifying a variable time-step computed from a CFL criterion
CFL_Min = 0.05                                   ,!--- Minimum value of the CFL criterion imposed by the user when the simulation starts
CFL_Max = 0.4                                    ,!--- Maximum value of the CFL criterion imposed by the user after n time iterations (here n= 100, see the next parameter)
Iterations_For_Timestep_Linear_Progress= 100     ,!--- Number of time iterations over which the CFL criterion increase linearly between CFL_Min and CFL_Max
Simulation_Backup_Rate                 = 1000    ,!--- Recording rate (in time-iteration units) for generating backup files (save_fld_xxxxx_y.d , save_var_xxxxx_y.d)
Simulation_Checking_Rate               = 200     /!--- Recording rate (in time-iteration units) for writing some relevant check data in a file checkcalc_xxxxx.d


The second example corresponds to a restart of the previous simulation with a uniform time step.

&Simulation_Management Restart_Parameter= 3             ,!--- Option value for resuming the simulation from the end of a previous computation.
Steady_Flow_Stopping_Criterion_Enabled = .false. ,!--- Stop criterion for steady flows. When it is enabled, residues between two successive flow fields are computed
Steady_Flow_Stopping_Criterion = 1.D-20          ,!--- convergence tolerance threshold for a steady flow solution (it works only when the previous parameter is enabled)
Temporal_Iterations_Number = 1000                ,!--- maximum value of time iterations before stopping the computation
Final_Time = 6.D+01                              ,!--- Maximum value of time before stopping the computation
TimeStep_Type = 0 ,                              ,!--- Option value for specifying a constant time-step
Timestep_Max = 1.e-3,                            ,!--- Value of the time step
Iterations_For_Timestep_Linear_Progress= 100     ,!--- Number of time iterations over which the CFL criterion increase linearly between CFL_Min and CFL_Max
Simulation_Backup_Rate                 = 1000    ,!--- Recording rate (in time-iteration units) for generating backup files (save_fld_xxxxx_y.d , save_var_xxxxx_y.d)
Simulation_Checking_Rate               = 200     /!--- Recording rate (in time-iteration units) for writing some relevant check data in a file checkcalc_xxxxx.d
Fields_Recording_Rate = 1.D+00 ,
Probe_Recording_Rate                   = 10     ,
Start_Time_For_Statistics= 1.D+2               ,
Time_Range_Statistic_Calculation = 1.D+00  /

• For explicit schemes, the CFL criterion also depends on the viscous/diffusive time scales as well as the space dimension of the problem. As a consequence, the CFL value prescribed is generally between $0.5^{n-1}$ and $0.5^n$, where n is the dimension of the problem.