This page summarizes some key points for using the code Sunfluidh in order to better understand the use of Sunfluidh.
The computational domain is the discrete space where equations are solved for flows simulations.
It is defined with the namelist “ Domain_Features ”. This namelist contains every data to set up the domain size, the meshsize (the number of cells per direction) and the grid type (regular or not regular). If the grid is regular, every cells have the same size along a given direction. In this case, Sunfluidh builds directly the grid. If the grid is non regular, you should generate speficic files with the mesh generator MESHGEN. These specific files are read by Sunfluidh at the beginning of the computation.
The spatial discretization of equations is carried out on a staggered grid :
The code uses ghost-cells at the domain's ends in order to handle the boundary conditions. These ghost-cells are placed around the computational domain, which is plotted with red lines in the next figure.
This part is particularly delicate. Please, spend time to read the three sub-sections just below about the boundary conditions and pay attention to the different examples proposed.
By default, the computational domain is an enclosed cavity : the domain ends are walls. New boundary conditions can be defined in the data file in place of the default ones by means of the namelists :
The inlet/outlet boundary conditions overwrite the default wall conditions only on areas defined by the user. Domain ends can be therefore defined from several types of boundary conditions (inlet/wall, outlet/wall, … see here for some examples.
The “border” boundary conditions overwrite the whole specified domain end.
Wall boundary conditions can be specified for different physical quantities with the following namelist :
If you do not specify any wall boundary conditions or “border” boundary conditions in the input data file, Sunfluidh assumes default boundary conditions which are :
Immersed bodies can be placed in the computational domain in order to build more complex flow geometries. Several geometries are available :
These data setup can be used in 2D and 3D configurations.
You can build different sets of wall boundary conditions for the velocity components and temperature from the namelists previously named (Velocity_Wall_Boundary_Condition_Setup, Heat_Wall_Boundary_Condition_Setup). Each set must be tagged by means of the indentifier “Wall_BC_DataSetName”:
The namelists of immersed bodies also get an indentifier “Wall_BC_DataSetName” which can be named with the tag corresponding to the appropriate wall boundary conditions.
The fluid properties are defined with the namelist Fluid_Properties .
It is not mandatory to set up all the data of the namelist. Only the data of interest must be considered, the other ones can be ignored.
You find here some examples :
For an incompressible fluid without heat transfer
&Fluid_Properties Reference_Density= 1.0 , Reference_Dynamic_Viscosity = 3.D-03 /
For an incompressible fluid with heat transfer
&Fluid_Properties Heat_Transfer_Flow = .true. , Reference_Density= 1.0, Reference_Temperature= 1.0 , Reference_Dynamic_Viscosity= 0.71D-02 , Reference_Heat_Capacity= 1.0. , Prandtl = 0.71 , Thermal_Expansion_Coefficient= 1.0 /
The initialization procedure relies on specific namelists :
These namelists propose several ways for initializing the fields of velocity, temperature, species mass fractions, etc …
The data set up that refers to the time step is in the namelist Simulation_Management. Two ways are possible :
Sunfluidh can provides various results of simulation :
Information on these results is provided on the page "Sunfluidh output files".
Three possibilities exist for stopping the simulation by means of data present in the namelist Simulation_Management :
The first criterion statisfied among the three ones stops the simulation.