Différences

Ci-dessous, les différences entre deux révisions de la page.

--- sunfluidh:sunfluidh_tutorials [2017/09/29 16:55] – yann
+++ sunfluidh:sunfluidh_tutorials [2020/01/30 11:31] (Version actuelle) – [Data setup] yann
@@ Ligne 18: / Ligne 18: @@
 The computation is on a 2D heated back-facing step flow. The temperature of the bottom and top walls is imposed to $T_c$ and the temperature of the step walls is $T_h$. The inflow is fixed with an uniform velocity profile $U_b$ at temperature $Tc$. We consider an incompressible flow under the Boussinesq hypothesis : the physical properties are constant and the thermal buoyancy effect is modelised by the Boussinesq hypothesis :
 $F_b= -\rho_0.\beta.g_0.(T - T_0)$ (see the page [[ Gravity_Namelist | Gravity ]] for more details).
-We suppose the fluid as a perfect gas. As a consequence, $\beta= \frac{1}{T_0}$
+We suppose the fluid is air that behaves as a perfect gas. As a consequence, $\beta= \frac{1}{T_0}$
 {{ :sunfluidh:heatedbackfacingstepflow.jpg?direct&600 |}}
+__The governing equations for incompressible flows are shown [[sunfluidh:sunfluidh_link_equations_data_set|here]]__.
 ==== Dimensionless data ====
@@ Ligne 61: / Ligne 63: @@
     * [[ tuto1_forces |Data set on forces on the fluid]]
     * [[ tuto1_boundaryconditions |Data set on the boundary conditions]]
-    * [[ tuto1_boundaryconditionss |Data set on the boundary conditions]]
     * [[ tuto1_numericalmethods |Data set on the numerical methods]]
     * [[ tuto1_simulationcontrol|Data set on the simulation control]]
     * [[ tuto1_outputdata |Data set on the output data]]
+<note>
+Boundary conditions can be difficult to understand. Some help can be find through [[ :sunfluidh:Examples_wall_bc | some examples illustrated here]].
-==== 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 more information on this data set, [[sunfluidh:simulation_management_setup_namelist|click here]].
-<note important>
-Keep in mind the time step must be chosen with caution because it can generate numerical instabilities when it is too much large. The numerical stability depends on the property of the numerical methods used for solving the conservation equations It often relies on the CFL criterion which have not to exceeded a reference value. This value depends on the numerical scheme properties as well as the computational problem.
-   * For semi-implicit schemes proposed here, a maximum CFL-value about 0.5 is generally prescribed for usual computations, but it could be smaller for problems with strong gradients.
-   * 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.
-When the time-step value is constant, the user can verify if the CFL criterion is respected by checking regularly the file checkcalc_xxxxx.d
 </note>
-==== Output data ====
-Here we show an example of usual data acquisition :
-   * Instantaneous fields
-   * Statistical fields
-   * Time series from probes located at specific positions
-The various parameters related to each type of output data are originally splitted by topic in the appropriate namelist. For a sake of clarity, they are directly regrouped for each type of output data as shown here :
-For instantaneous fields
-   &Field_Recording_Setup         Precision_On_Instantaneous_Fields= 2 /                  !--- option value for writing results in double precision (1 = single precision)
-   &Simulation_Management         Fields_Recording_Rate = 1.0D-00 /                       !--- Recording rate (in time unit)
-   &Instantaneous_Fields_Listing  Name_of_Field = "U" , Recording_Enabled = .true.  /     !--- Recording of the first velocity component enabled
-   &Instantaneous_Fields_Listing  Name_of_Field = "V" , Recording_Enabled = .true.  /     !--- Recording of the second velocity component enabled
-   &Instantaneous_Fields_Listing  Name_of_Field = "W" , Recording_Enabled = .false. /     !--- Recording of the Third velocity component disabled
-   &Instantaneous_Fields_Listing  Name_of_Field = "T" , Recording_Enabled = .true.  /     !--- Recording Temperature enabled
-   &Instantaneous_Fields_Listing  Name_of_Field = "P" , Recording_Enabled = .true.  /     !--- Recording Pressure enabled
-For statistical fields
-   &Simulation_Management Start_Time_For_Statistics= 1.D+2               ,          !--- Start time for computing the statistical fields
-                          Time_Range_Statistic_Calculation = 1.D+00      /          !--- time range over which the statistical field computation is performed.
-                                                                                          When it has been covered, the results are recorded and a new statistical computation starts again
-   &Field_Recording_Setup      Precision_On_Statistical_Fields= 2 ,                 !--- option value for writing results in double precision (1 = single precision)
-                               Time_Statistics_Enabled= .true.    ,                 !--- time statistics  are performed (true) - classical statistics (false)
-                               Sample_Rate_For_Statistics= 1      ,                 !--- Sample rate (in time iteration unit)
-                               Statistic_Space_Average_Type= "NO_SPACE_AVERAGE" /   !--- option on spatial averaged fields
-   &Statistical_Fields_Listing  Name_of_Field = "<U>   " , Recording_Enabled = .true.  /   !---- Averaged I-velocity component
-   &Statistical_Fields_Listing  Name_of_Field = "<V>   " , Recording_Enabled = .true.  /   !---- Averaged J-velocity component
-   &Statistical_Fields_Listing  Name_of_Field = "<P>   " , Recording_Enabled = .true.  /   !---- Averaged pressure
-For time-series from probes
-                                                                         U    , V     , W      , T      , P     , RHO
-   &Probe_Quantities_Enabled  Temporal_Series_For_Quantity_Enabled(:)= .true. , .true., .false., .false., .true., .false.    /    !--- Selection of physical quantities
-   &Simulation_Management Probe_Recording_Rate                       = 10                                                     /   !--- Recording rate (in time-iteration unit)
-   &Probe_Location  Xi= 2.0 , Xj= 1.5 , Xk= 0.0 /       !---coordinates of probe 1
-   &Probe_Location  Xi= 3.0 , Xj= 1.0 , Xk= 0.0 /       !---coordinates of probe 2
-<note important>
-Any information about these namelist are available here :
-   * [[Simulation_Management_Setup_Namelist|Simulation_Management]]
-   * [[Field_Recording_Setup_Namelist_Setup|Field_Recording_Setup]]
-   * [[Instantaneous_Fields_Listing_Namelist_Setup|Instantaneous_Fields_Listing]]
-   * [[Statistical_Fields_Listing_Namelist_Setup|Statistical_Fields_Listing]]
-   * [[Probe_Quantities_Enabled_Setup_Namelist|Probe_Quantities_Enabled]]
-   * [[Probe_Location_Setup_Namelist|Probe_Location]]
-</note>