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CONTROL AND DATA FILES
◦ RoeMagKin: The standard Roe solver is extended to transport passively a magnetic
field. This is a test implementation to check if the general magnetic field handling
works. For proper MHD simulations use RoeMHD instead.
◦ RoeMHD: Compile the MHD HLL solver.
• character hdsplit:
With this parameter the type of the hydrodynamics operator (directional) splitting scheme
can be specified as in
character hdsplit f=A80 b=80 n=’Hydrodynamics directional splitting scheme’ &
c0=’123 (default): directional splitting’ &
c1=’unsplit: new unsplit operator’
123
Possible values are
◦ 123: (default) The standard directional splitting is activated, where the 1D operators
for the individual directions are applied in the given order. So far, only the order 123
is possible.
◦ unsplit: The standard Roe solver is applied. However, the changes from the individual steps are computed from (and applied to) the same model configuration. The
result is an unsplit scheme.
• character reconstruction:
This parameter determines the order and “aggressiveness” of the reconstruction scheme
with e.g.
character reconstruction f=A80 b=80 n=’Reconstruction method’ &
c0=Constant c1=Minmod/VanLeer/Superbee c2=PP
Minmod
Possible values are
◦ Constant: The run of the partial waves inside the cells is assumed to be constant. A
highly dissipative first order scheme results. This values will usually only be used for
test (or comparison) purposes.
◦ Minmod: Chooses the smallest slope which still results in a second order scheme. It is
the most diffusive (and most stable) one in this class.
◦ VanLeer: (default) The recommended second order scheme.
◦ Superbee: The “most aggressive” stable 2nd order scheme. It results in the steepest
shocks, which works well in some test cases but might be to difficult for the radiation
transport module to handle.
◦ PP: Chooses the piecewise parabolic reconstruction of the PPM scheme (“Piecewise
Parabolic Method”, Colella & Woodward 1984). Results in 3rd order accuracy for the
advection. This method can only be used with the standard hdscheme Roe, not with
hdscheme RoeMHD.
Usually, the VanLeer reconstruction is a good choice. If a more stable (and diffusive) scheme
is needed, take Minmod. The PP reconstruction gives the highest accuracy. However, it tends
to produce somewhat “noisy” models with small wiggles e.g. in the velocity. The 2nd order
piecewise parabolic reconstruction (PP) is not implemented in the MHD module. By specifying e.g. VanLeer Superbee it is possible to use the VanLeer scheme for the hydrodynamics
scheme as such and Superbee only for the advection of additional quc quantities.