Documentation du code de simulation numérique SUNFLUIDH

Meshgen is a modest mesh generator for cartesian grid. The principle is very simple :

• Each direction {x,y,z} (or {r,$\theta$,z} in cylindrical geometry) is represented by a line.
• Each line can be splitted in several parts over which a distribution law is applied in order to build the discretization nodes.
• Following the CFD code used, these nodes have different definitions :
  • For Chorus, they are the cell centers.
  • For Sunfluidh, they are the cell-face locations.
• Several distribution laws are available
  • Geometric functions
  • Hyperbolic tangent functions
  • Cosine function

After downloading the Meshgen project from the server forge by means of svn:

• go to the directory MESHGEN/TRUNK/SOURCES
• Run the command make: The executable file meshgen.x is created.

The grid parameters are set in the input data file “data_meshgen.dat”. A simple example of a 2D grid is given just below :

• The cell size is variable along the I-direction.
  • The I-line is split in two equal parts.
  • The function “TANH_ONE_SIDE” is applied over each part, with a reverse distribution over the 2nd part. This way is useful to define a perfect symmetrical distribution in regard to the mid-plane.
• The grid is regular along the J-direction

data_meshgen.dat

==============================================================================================================
            DATA FILE FOR THE MESH GENERATOR MESHGEN (DESCRIPTIONS OF DATA ARE GIVEN BELOW)
==============================================================================================================
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Blocks of data are associated to segments along a specific direction (There are as many blocks as segments)
See below the TEMPLATES to select your own block of data associated to the selected distribution law)
-------------------------------------------------------------------------------------------------------------
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I-DIRECTION
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Choice of the metric system :  in meter or dimensionless  (0)  - angular in degrees (1)     :
&METRIC_UNIT         Type_of_Metric= 0 /
&MESH_FUNCTION_DATA Function_Name="TANH_ONE_SIDE" Number_of_Cells= 64   Length= 0.5  Left_Cell_Size= 1.2d-03 Reverse_Ordering= .false. /
&MESH_FUNCTION_DATA Function_Name="TANH_ONE_SIDE" Number_of_Cells= 64   Length= 0.5  Left_Cell_Size= 1.2d-03 Reverse_Ordering= .true. /
&MESH_FUNCTION_DATA End_of_Data_Block = .true./
---------------------------------------
J-DIRECTION
---------------------------------------
Choice of the metric system :  in meter or dimensionless  (0)  - angular in degrees (1)     :
&METRIC_UNIT         Type_of_Metric= 0 /
&MESH_FUNCTION_DATA  Function_Name="REGULAR"           Number_of_Cells= 128  Length= 1.0   Reverse_Ordering= .false. /
&MESH_FUNCTION_DATA End_of_Data_Block = .true./
---------------------------------------
K-DIRECTION
---------------------------------------
 
&MESH_FUNCTION_DATA End_of_Data_Block = .true./
 
END OF FILE

In the data file, each block of data is attributed to a direction (I,J or K).
Each direction can be split in several parts (segments) on which a specific distribution law is applied in order to place the discrete nodes.
Each distribution law is associated to a function defined by a namelist. The available functions are :

• Regular function (Function_name= REGULAR_MESH)
• Hyperbolic tangent function “one side” (Function_Name= TANH_ONE_SIDE_MESH)
• Hyperbolic tangent function “two sides” (Function_Name= TANH_TWO_SIDES_MESH)
• Gauss-Lobatto distribution (Function_Name= GAUSS_LOBATTO_MESH)
• Geometric series “type 1” (Function_Name= GEOMETRIC_SERIE_1_MESH)
• Geometric series “type 2” (Function_Name= GEOMETRIC_SERIE_2_MESH)

These functions get a specific data set :

• Number_of_Cells : Number of cells over the segment (for all functions).
• Length : Length of the segment (for all functions).
• Left_Cell_Size : Reference size of the cell placed at the left tip of the segment (for all functions except the regular function)
• Right_Cell_Size : Reference size of the cell placed at the right tip of the segment (for hyperbolic function “two sides” and geometric series “Type 1” only)
• Reverse_Ordering : Reverse the ordering of the distribution if set to .true.
• End_of_Block_Data : logical set to .true. to declare the end of a data structure (by default it set to .false. by the program)

A template each function is given here