"Optional title"
coid
entype, enid, $T_{amb}$, $d_{max}$, $\Delta t_{update}$
##### Parameter definition
VariableDescription
coid Command ID
entype Entity type
options: FS, G, GS, P, PS, ALL
enid Entity identification number
$T_{amb}$ Ambient temperature
$d_{max}$ Interaction cut-off distance
default: not used
$\Delta t_{update}$ Interaction list update interval
default: no update
##### Description

This command is used to define the thermal radiation interaction between surfaces. The radiating power $q$ per unit area from a surface is defined as:

$\displaystyle{q = \varepsilon \sigma T^4}$

where $\varepsilon$ is the emissivity (defined in PROP_THERMAL), $\sigma$ is the Stefan-Boltzmann constant and $T$ is the absolute temperature. Radiating energy can be absorbed by (and partially reflected from) surrounding surfaces that are in line-of-sight. The emissivity of a receiving surface controls the energy that is absorbed. Reflected energy can be transferred to surrounding faces that are in line-of-sight.

The ambient temperature $T_{amb}$ constitutes an external (background) heat source.

##### Example

Thermal radiation and interaction between a hot and a cold plate. The emissivity of the cold plate is low and a significant amount of energy is reflected back to the hot plate. Hence, the back face of the hot plate cools off quicker than the front face.

*UNIT_SYSTEM
SI
*TIME
100.0, 0, 0, 1.0e-3
#
# --- SENSOR ---
#
*OUTPUT_SENSOR
"Sensor 1"
1, 1, -0.03,
"Sensor 2"
2, 1, -0.01
#
# --- MESH ---
#
*COMPONENT_BOX
"Hot"
1, 1, 2, 6, 6
-0.03, -0.1, -0.1, -0.01, 0.1, 0.1
*COMPONENT_BOX
"Cold"
2, 2, 2, 6, 6
0.01, -0.1, -0.1, 0.03, 0.1, 0.1
#
# --- MATERIAL ---
#
*MAT_RIGID
1, 3000.0, 0, 0, 0, 1
*PROP_THERMAL
1, 0, 400.0, 1.0, 0, 0, 1.0
*MAT_RIGID
2, 3000.0, 0, 0, 0, 2
*PROP_THERMAL
2, 0, 400.0, 1.0, 0, 0, 0.1
#
# --- PART ---
#
*PART
"Hot"
1, 1
"Cold"
2, 2
#
# --- INITIAL CONDITION ---
#
*INITIAL_TEMPERATURE
P, 1, 0, 1273.15
*INITIAL_TEMPERATURE
P, 2, 0, 273.15
#