/RADIATION
Block Format Keyword Describes the imposed radiation flux to environment.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/RADIATION/Radiative_Flux_ID/unit_ID  
Radiative_Flux_title  
surf_ID_{T}  fct_ID_{T}  sens_ID  
Ascale_{x}  Fscale_{Y}  T_{start}  T_{stop}  $\epsilon $ 
Definitions
Field  Contents  SI Unit Example 

Radiative_Flux_ID  Imposed radiative flux
block identifier. (Integer, maximum 10 digits) 

unit_ID  Unit Identifier. (Integer, maximum 10 digits) 

Radiative_Flux_title  Imposed radiative flux
block title. (Character, maximum 100 characters) 

surf_ID_{T}  Identifier for surface
which absorbs thermal radiation. (Integer) 

fct_ID_{T}  Time function identifier
for the temperature of heat source
${T}_{\infty}$
. (Integer) 

sens_ID  Sensor
identifier. (Integer) 

Ascale_{x}  Abscissa (time) scale
factor for
fct_ID_{T}. Default = 1.0 (Real) 
$\left[\text{s}\right]$ 
Fscale_{Y}  Ordinate (temperature)
scale factor for
fct_ID_{T}. Default = 1.0 (Real) 
$\left[\text{K}\right]$ 
T_{start}  Start
time. (Real) 
$\left[\text{s}\right]$ 
T_{stop}  Stop
time. (Real) 
$\left[\text{s}\right]$ 
$\epsilon $  Emissivity
$\text{0}<\epsilon <1$
. (Real) 
Example (Thermal Loading)
#RADIOSS STARTER
#12345678910
/UNIT/12
unit for imposed radiation load
Mg mm s
#12345678910
/RADIATION/1/12
RADIATION from heat source
# surf_ID fct_ID sens_ID
5 2003 0
# ASCALE FSCALE TSTART TSTOP E
0 0 0 0 0.15
#12345678910
/FUNCT/2003
temperature of heat source function of time
# X Y
0 773
1 700
#12345678910
#ENDDATA
Comments
 The radiation
flux is calculated using:
(1) $$\phi =\epsilon \sigma \left({T}^{4}{\text{T}}_{\infty}^{4}\right)$$Where, T
 Temperature of the surface (surf_ID_{T}) which absorbs thermal radiation
 $\sigma $
 The StefanBoltzmann constant
(2) $$\sigma =\text{5}{\text{.669x10}}^{\text{8}}\text{}\frac{W}{{m}^{2}\cdot {K}^{4}}$$Since $\sigma $ is a constant which depends on the units, the unit system must be set correctly in /BEGIN and in the optional unit_ID which is used by the radiative flux block.
 Thermal radiation is only compatible with the finite element formulation for heat transfer.
 /RADIATION is not compatible with ALE applications (/ALE, /EULER). Thermal radiation will not be applied to ALE nodes or ALE elements.