7.1.18 Radiation-transport control (LHDrad only)

7.1.18.1 real c_radtvisdtau

Using the LHDrad module the limit in delta optical depth (rho*kappa*dx) below which the ``radiative temperature viscosity'' (=temperature smoothing) is to be applied can be set with e.g.

real c_radtvisdtau f=E15.8 b=4 &
  n='Optical depth limit for temperature viscosity' u=1
0.1

The introduction of this ``temperature diffusion'' is a somewhat desperate and inelegant attempt to improve the behavior of the Greens function (hot cells should be cooled, cool cells should be heated). This diffusion is necessary for not well resolved models. It is switched off with c_radtvisdtau $\leq$ 0.0.

7.1.18.2 real c_radtvis

Using the LHDrad module the amount of the ``radiative temperature viscosity'' (=temperature smoothing) can be specified e.g. with

real c_radtvis f=E15.8 b=4 n='Temperature viscosity' u=1
1.6

For well resolved models it should be switched off (with c_radtvis $\leq$ 0.0).

7.1.18.3 real c_radthintimefac

In the LHDrad module only the radiative time step restriction due to energy changes can be relaxed further in the optically thin by specifying e.g.

real c_radthintimefac f=E15.8 b=4 &
  n='time scale reduction in optically thin'                         u=1 &
  c0='range: 0.1 - 1.0, typically: 0.5'
 0.60

A value $\leq$ 0.0 or real c_radtvisdtau $\leq$ 0.0 switches off this relaxation.