====== CONRA ======
===== Description =====
2D boundary. The element is used to model convection and radiation between the structure and the environment. It is  defined by 1, 2, or 3 "real" nodes and 1 node representing the environment. \\
It can only be used with laws [[laws:raco|RACO]] and [[laws:copo1|COPO1]] (for pollution problems). \\ \\
If the element is connected to a [[laws:rayon|RAYON]] element, it must have 3 nodes. \\ \\
For pollution problems, these elements must be defined last. \\

Type: 111
Implemented by: R. Charlier, 1982
==== Files ====
Prepro: CONRAA.F \\
Lagamine: CONRAB.F
===== Input file =====
^ TITLE (A5)^^
|TITLE|"CONRA" in the first five columns|
^Line 2 (2I5)^^ 
|NELEM| Number of elements|
|NNODE| Total number of nodes (environment included)|
^Definition of the elements (5I5/4I5)^^
|NINTE|Number of integration points: \\ 2 or 3 for NNODE > 2 \\ 1 for NNODE = 2|
|LMATE| Material|
|NPOND| Ponderation index \\ = 0 for classic use (law [[laws:raco|RACO1]]) \\ = 1 for Upwind elements in a pollutant transport problem (law [[laws:copo1|COPO1]]), in that case NNODE must be equal to 2: one node that belongs to the convection-diffusion elements (CONV2, ADVE2, ELAN2) and one environment node.|
|NCOEL|Number of elements related to true nodes (1 to 4) - see Note [[elements:conra#(1) Explanation on NCOEL and ICAS|(1)]]|
|ICAS |For each NCOEL one must detail the topology of the related elements - see Note [[elements:conra#(1) Explanation on NCOEL and ICAS|(1)]]|
|NODES| List of nodes (4, 3 or 2) see <imgref image1>|
**Remark**: For a Eulerian Lagrangian analysis of pollution, the environment node must be positioned outside the structure. \\
<imgcaption image1|>{{  :elements:conra.png?700  |}}</imgcaption>

===== Results =====
|Sigma(1)|First part of the total flux (convection + radiation taken by diffusion in the domain)|
|Sigma(2)|Second part of the flux (taken by convection in the domain)|

=== (1) Explanation on NCOEL and ICAS ===
  * For the classic use: NCOEL = ICAS = 0
  * For a Eulerian Lagrangian analysis of pollution, NCOEL = 4 and ICAS = 0
  * For FUPG analysis of pollution, distinction between the following topologies:

|  **NCOEL = 1** \\ 1 solid element connected \\ to the real node  |{{:elements:conra_ncoel1.png?500|}}|
|  **NCOEL = 2** \\ 2 solid elements connected \\ to the real node  |{{:elements:conra_ncoel2.png?450|}}|
|  **NCOEL = 3** \\ 3 solid elements connected \\ to the real node  |{{:elements:conra_ncoel3.png?450|}}|
|  **NCOEL = 4** \\ 4 solid elements connected \\ to the real node  |  {{:elements:conra_ncoel4.png?250|}}  |
|  2 solid elements connected \\ to the real node \\ \\ Treated like the case \\ **NCOEL = 4** & ICAS = 0  |{{:elements:conra_ncoel4b.png?450|}}|