Summary: Modify the numerical relaxation for radiation heat flux.
Flag:
RadFluxRelax A
A = 0: the default relaxation is used for radiation heat flux (relax = 0.1)
A > 0: the relaxation on radiation heat flux = 0.A (For example, enter 45 to set a relaxation value of 0.45.)
Description:
Because the default of 0.1 is very conservative, this flag is seldom needed.
If the temperature changes too quickly in a radiation analysis, there are two techniques for ensuring solution stability:
1. Set the Max_Pseudo_Time_Step_Size to limit the allowable time step.
or
2. Set the ICS_RAD_NUMERATOR to control the time step limit. (Time step size = ICS_RAD_NUMERATOR/Tmax) ^4.
Where Tmax is the absolute max temperature. For example, if ICS_RAD_NUMERATOR is set to 2500, and Tmax = 1000K, then, the Time Step Size = (2500/1000)^4 = 39 seconds. This ensures that as the analysis gets hotter, the time step control gets more restrictive.