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--- doc:user:elements:boundaries:radiation [2013/07/10 11:56] – [Interaction] joris
+++ doc:user:elements:boundaries:radiation [2026/07/30 08:56] (current) – boman
@@ Line 1: / Line 1: @@
+====== Radiative Material ======
+<note important>
+This Documentation refers to Metafor version >= 3593.
+for more informations on changes see [[https://gitlab.uliege.be/am-dept/MN2L/oo_meta/-/merge_requests/167|MR !167]] for technical informations).
+for a Metafor version < 3593, please refers to this [[radiation_pre3593|page]].
+</note>
+===== RadiativeMaterial =====
+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.
+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)
+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.
+  mat = materset.define(no, RadiativeMaterial )
+  mat.put(param1, value1)
+  mat.depend(param1, fct1, Lock1)) #optional
+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) |
+=== Parameters ===
+^   Name                                          ^     Description       ^  Dependency ^
+| ''BOLTZMANN_CST'' | Stefan-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  |
+| ''RAY_CELSIUS''   | flag to chose Themperature unit system of the test (default : Kevin => False)     |  -  |