====== Radiation ======

===== Materials=====     

Since radiation interactions are boundary conditions interactions (''LoadingInteraction''), no materials must be associated to the element.

===== Element =====

Therefore, the first step consist in defining an ''[[doc:user:elements:general:def_element_properties|ElementProperties]]'', as

  prp = ElementProperties(typeEl)
  prp.put(param1, value1)
  prp.depend(param1, fct1, Lock1)) #optional
  ...

where
|''typeEl'' | desired element (for example ''Tm[2]Rayonnement[2|3]DElement'')|
|''param1''| name of the property associated to the element (for example ''RAY_EMISSIVITY''|
|''value1''| value of the corresponding property |
|''fct1''| function which characterizes the dependency of the property (optional: no fct if no dependency) |
|''Lock1''| [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

==== Tm[2]Rayonnement[2|3]DElement ====

:!: Using radiation elements requires the use of Kelvin in the entire model !!!

Thermal radiation element with given room temperature. First or second degree.

<note>TODO : Ajouter équations de rayonnement </note>

=== Parameters ===
^   Name                                          ^     Description       ^  Dependency ^
| ''STIFFMETHOD'' | Method used to compute the stiffness matrix\\= ''STIFF_ANALYTIC'' : analytic matrix (default)\\ = ''STIFF_NUMERIC''  : numerical matrix |  -  |
| ''BOLTZMANN_CST''| Boltzmann Constant (required to set units)\\ =  $ 5.67e^{-8}  W/m^2K^4 $\\ =  $ 5.67e^{-11}  mW/mm^2K^4$|  Set |
| ''RAY_EMISSIVITY''| Relative emissivity between two gray bodies (solid / room)\\ $\epsilon = \frac{\epsilon_1 * \epsilon_2}{\epsilon_1 + \epsilon_2 - \epsilon_1 * \epsilon_2}$    |  time | 
| ''RAY_TEMP_AMB''  | Room temperature (K)  |  time |
| ''NPG''    | Number of integration points (default : tm : 2 / tm2 : 3)    |  -  |


===== Interaction =====

The interaction is defined as:

  load = LoadingInteraction(no)
  load.push(gObject1)
  load.push(gObject2)
  ...
  load.addProperty(prp)
  interactionset.add(load)

where

| ''no''       | number of the ''Interaction''  | 
| ''gObject1'', ''gObject2''  | mesh geometric entity where the boundary conditions are applied  | 
| ''prp''      | [[doc:user:elements:general:def_element_properties|Properties]] of [[#Element|boundary condition elements]] to generate |