====== RAYON ======
===== Description =====
Radiative exchange between walls or between wall and environment. \\ Used with 3 node [[elements:conra|CONRA]] elements. \\
Type: 112 \\
Implemented by: M. Bourdouxhe, 1987
==== Files ====
Prepro: RAYONA.F \\
Lagamine: RAYONB.F
===== Input file =====
^ TITLE (A5)^^
|TITLE|"RAYON" in the first 5 columns|
^Control data (I5)^^
|NELEM|Number of elements|
^Definition of the elements (3I5/6I5)^^
|NINTE|Number of integration points from 1 to 10|
|LMATE|Material|
|INDIC|Connction type \\ = 0 → exchange between 2 faces belonging to the same structure ([[elements:conra|CONRA]] element) \\  = 1 → Radiation towards a fictive surface (leak flow or symmetry) \\  = 2 → Radiation between a face representing the symmetry and a face representing a leak flow|
|NODES(6)| Definition of the nodes|
**Examples for INDIC**
^INDIC^Examples^Figure^
|  0  |Example 1:    4    8 \\ \\ Link between 2 faces of the structure |{{:elements:rayon1.png?200|}}| 
|  1  |Example 2: 10 16 14 9 - Description of the leak flow towards the fictive face \\ \\ Example 3: 10 15 1 14 - Description of the symmetry flow towards the fictive face|{{:elements:rayon2.png?350|}}|
|  2  |Example 4: 15 16 1 14 14 9 - Link between the leak flow and the symmetry flow |:::|

===== Results =====
  * Sigma(1): flow unaffected by the viewing factor
  * Sigma(2): flow affected by the viewing factor and the area of the element ($A_1 F_{12}=A_2 F_{21}$)

===== Remarks =====
  - CONRA: Structure to the left in relation to the numbering direction {{:elements:rayon3.png?150|}}
  - RAYON: Face describing the symmetry and the leak flow to the right in relation to the numbering direction \\ {{:elements:rayon4.png?400|}}