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--- doc:user:elements:boundaries:radiation [2026/07/29 11:09] – papeleux
+++ doc:user:elements:boundaries:radiation [2026/07/30 08:56] (current) – boman
@@ Line 1: / Line 1: @@
-====== Radiation ======
+====== Radiative Material ======
 <note important>
@@ Line 8: / Line 8: @@
 </note>
-===== Materials=====
+===== RadiativeMaterial =====
-Since radiation interactions are boundary conditions interactions (''LoadingInteraction''), no materials must be associated to the element.
+The ''RadiativeMaterial'' is implemented to take into account the heat exchange between the boundary of a mesh and the surrounding atmosphere (at uniform Temperature) without taking into account any view factor or self exchange between mesh.
-===== Element =====
+The heatFlux (W/m²) is equal to
+$flux = -\sigma \epsilon (T^4-T_{amb}^4)$
+with :
+  * $\sigma$ : the Stefan-Boltzmann Constant (5.67 × 10-8 W/m²K4)
+  * $\epsilon$ : relative emissivity parameter (1)
+  * $T$ : temperature at the integration point (K)
+  * $T_{amb}$ : Room temperature (K)
-Therefore, the first step consist in defining an ''[[doc:user:elements:general:def_element_properties|ElementProperties]]'', as
+It is designed to work with ''Tm(2)Boundary2D(/3D)Element''. By default, the surrounding model has to be defined in Kelvin, but defining the parameter ''RAY_CELSIUS'' to ''True'' allows using it in a Celsius defined test.
-  prp = ElementProperties(typeEl)
-  prp.put(param1, value1)
-  prp.depend(param1, fct1, Lock1)) #optional
-  ...
-where
+  mat = materset.define(no, RadiativeMaterial )
-|''typeEl'' | desired element (for example ''Tm[2]Rayonnement[2|3]DElement'')|
+  mat.put(param1, value1)
-|''param1''| name of the property associated to the element (for example ''RAY_EMISSIVITY''|
+  mat.depend(param1, fct1, Lock1)) #optional
-|''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 !!!
+where
+|''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) |
-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'' | Stefan-Boltzmann Constant (required to set units)\\ =  $ 5.67e^{-8}  W/m^2K^4 $\\ =  $ 5.67e^{-11}  mW/mm^2K^4$|  Set  |
-| ''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_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  |
-| ''RAY_TEMP_AMB''  | Room temperature (K)  |  time |
+| ''RAY_CELSIUS''   | flag to chose Themperature unit system of the test (default : Kevin => False)     |  -  |
-| ''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 |