hdsplit=CTU,
the chunk size in 
direction can be specified independently.
The default is to used integer n_hydcellsperchunk.
The approximate number of grid cells per chunk can be specified e.g. with
integer n_hydcellsperchunk.
However, as accesses to chunks in direction span many memory pages,
the access time is longer than for properly aligned chunks in 
direction
and somewhat larger (twice...) values might be optimal.
Alternatively, a value of n_hydcellsperchunk2=1 causes a two-stage
access where first an entire 2D slice is transposed and copied to achieve
properly alignment and then the normal chunk size (specified with integer n_hydcellsperchunk)
is used in a consecutive step.
direction can be specified independently.
The default is to used integer n_hydcellsperchunk.
The approximate number of grid cells per chunk can be specified e.g. with
integer n_hydcellsperchunk.
However, as accesses to chunks in direction span many memory pages,
the access time is longer than for properly aligned chunks in direction
and somewhat larger (twice...) values might be optimal.
Alternatively, a value of n_hydcellsperchunk3=1 causes a two-stage
access where first an entire 2D slice is transposed and copied to achieve
properly alignment and then the normal chunk size (specified with integer n_hydcellsperchunk)
is used in a consecutive step.
hdscheme = Roe and hdtimeintegrationscheme = RungeKutta2
(and only there), the default number of Runge-Kutta sub steps
can be increased relative to the default value 2 to improve the performance
in the case of a large ratio of radiative to hydrodynamical time scales.
The parameter can be set e.g. with
2: (default) The standard predictor-corrector 2nd-order Runge-Kutta step number.
Cost: 2; advance 1; C_hydSoundCourantMax=1/3 =0.333
3: Typical recommended value.
Cost: 3; advance 2; C_hydSoundCourantMax=1/3*(3/2)^(1/3)=0.381
5: Rather large, still sensible value.
Cost: 5; advance 4; C_hydSoundCourantMax=1/3*(5/4)^(1/3)=0.358
real c_hydlowmachcsfactor.
This is in fact a tiny modification of the Roe solver but changes its behavior
significantly and requires
(for C_hydLowMachcsFactor>0.0)
hdsplit=unsplit and
hdtimeintegrationscheme=RungeKutta2 or hdtimeintegrationscheme=RungeKutta3.
The value can be set e.g. with
0.0: The extra reduction factor is not applied.
This is the standard Roe scheme.
It is still the recommended default, excepd for very-low-Mach-number flows.
1.0: Smallest meaningful value to switch on the reduction.
2.0: Reasonable value
5.0: Rather large value
real c_hydlowmachcsfactor.
With real c_hydlowmachcsbase, a minimum value can be chosen as, e.g., in
0.0: The extra reduction factor is not applied.
This is the standard Roe scheme.
It is still the recommended default, excepd for very-low-Mach-number flows.
<1.0E-06: Dangerously small values
1.0E-06: Default
0.001 to 0.02: Reasonable values
1.0: Switch off the low-Mach-number sound-speed reduction
real c_hydsmallfluctfactor, a scaling factor can be chosen to
fine tune the regime of the small-fluctation treatment, as, e.g., in
<1.0: Extend the small-fluctuation treatment towards larger fluctuations.
This can can result in a nicer entropy profile but might be unstable.
1.0: Default
0.5, 1.0, 2.0, 5.0: Reasonable values
>1.0: Extend the large-fluctuation treatment towards smaller fluctuations.
This improves stability but leads to artefacts in the entropy stratification
under near-adiabatic conditions.
between neighboring cells).
This value can be set e.g. with
0.0: Slope reduction switched off.
Original reconstruction is used.
0.02: Moderate slope reduction in case of large density jumps.
0.10: More pronounced slope reduction in case of strong density contrast.
FRcont have the option to make
the reconstruction even more continuous in the case of very low Mach numbers,
controlled with C_RecContShift and C_RecContSteep.
The value can be set e.g. with
0.0: No attempt is made to make the reconstruction more continuous.
The original reconstruction is used.
0.1: Make the transition to a smoother reconstruction at lower Mach numbers.
1.0: Reasonable value.
10.0: Make the transition to a smoother reconstruction at higher Mach numbers.
FRcont have the option to make
the reconstruction even more continuous in the case of very low Mach numbers,
controlled with C_RecContShift and C_RecContSteep.
The value can be set e.g. with
0.0: No attempt is made to make the reconstruction more continuous.
The original reconstruction is used.
0.01: Make the transition to a smoother reconstruction steeper
(at even lower Mach numbers)
0.1: Reasonable value.
1.0: Make the transition to a smoother reconstruction smoother
VAweno and HBweno
(but not the ``Frankenstein'' versions like FRweno)
allow to set the basic weights for the stencil of each of the three polynomials.
This possibility is given mainly for development purposes.
Users will likely not change the default values.
The specifiers ``central'' and ``right'' refer to the central and right stencil for finding the value at the right side of a cell. The ``central'' stencil includes the left and right neighbor cells. The ``right'' stencil is shifted on point to the right. The ``left'' stencil is shifted on point to the left, furthest away from the (right) cell boundary under consideration. The value for the central stencil can be set e.g. with
0.3333333: Give the central polynomial 1/3 of the total weight.
Together with c_recwenoweightright=0.5 (Sect.7.1.9.11),
this attributes equal weights to all three stencils.
0.5: Low, but reasonable value.
0.6: Recommended value. Found by a number of empirical tests to be a good choice
together with c_recwenoweightright=0.6666666 (Sect.7.1.9.11).
1.0: Give all weight to the central polynomial.
This essentially kills the central idea of the WENO scheme and only
makes sense for test purposes.
VAweno and HBweno
(but not the ``Frankenstein'' versions like FRweno)
allow to set the basic weights for the stencil of each of the three polynomials.
The value for the ``right'' stencil can be set e.g. with
0.0: Give all weight (that does not go to the central polynomial) to the left polynomial.
For test purposes.
0.5: Give left and right polynomial equal weight.
0.6666666: Recommended value. Found by a number of empirical tests to be a good choice
together with c_recwenoweightcenter=0.6 (Sect.7.1.9.10).
1.0: Give all weight (that does not go to the central polynomial) to the right polynomial.
For test purposes.
HBweno
compared to the standard ``Vanilla'' WENO scheme VAweno.
The value of the parameter can be set e.g. with
0.0: No additional smoothing.
This reduces HBweno to the (faster) VAweno.
For test purposes only.
1.0: Weak smoothing
4.0: Reasonable value.
16.0: Strong smoothing.
c_reccontshift (Sect.7.1.9.8)
is used. Typically,
c_recwenopsifactor 
c_recwenopsifactor/c_reccontshift.
Normal, ' ': Compute flux of transversal momentum with standard Roe treatment
(old, default)
CA1: Compute flux of transversal momentum with consistent advection, version 1.
Use mass flux and upwind density to determine flow speed.
Actually recompute transversal velocities.
CA2: Compute flux of transversal momentum with consistent advection, version 2.
Use mass flux and Roe-mean density (
) to determine flow speed.
Actually recompute transversal velocities.
CA3: Compute flux of transversal momentum with consistent advection, version 3.
Use mass flux and upwind density to determine flow speed.
Compute transversal momentum fluxes from mass flux and diffusive momentum flux.
CA4: Compute flux of transversal momentum with consistent advection, version 4.
Use mass flux and Roe-mean density () to determine flow speed.
Compute transversal momentum fluxes from mass flux and diffusive momentum flux
(recommended).
Normal.
The four new advection types are made of to choices for the way to compute
the effective flow speed across a cell boundary (different density values
can be used) and two ways to compose the final transversal momentum fluxes.
Version CA4 is recommeded.
This parameter is not recognized by the MHD module.
Normal, ' ': Compute entropy-wave flux with standard Roe treatment
from pressure and density,
(old, default).
Entropy1: Compute entropy-wave flux from entropy.
This only works well for small Mach numbers.
Entropy2: Compute entropy-wave flux from entropy and pressure.
Entropy3M: Compute entropy-wave flux from entropy, pressure, and density.
In fact, an cases Normal and Entropy1 are interpolated according to
the Mach number.
Entropy3Ms: Compute entropy-wave flux from entropy, pressure, and density.
In fact, an cases Normal and Entropy1 are interpolated according to
the Mach number and entropy fluctuations.
Entropy3gMps: Compute entropy-wave flux from entropy, pressure, and density.
In fact, an cases Normal and Entropy1 are interpolated according to
the Mach number and fluctuations in pressure (directly and after subtracting
the hydrostatic pressure correction) and entropy. This case is recommended.
Normal computation with the standard Roe procedure is optimized for shocks
and works also for small fluctuations in density and pressure.
However, in the case of a nearly adiabatic stratification, the density and pressure
fluctuations between adjacent depth points induce some spurious fluxes.
These are avoided by reconstructing the entropy directly (Entropy1).
However, that does not work well for shocks.
Therefore, an interpolation between the standard reconstruction based on
pressure and density and another one based on entropy is recommended
(Entropy3gMps).
This parameter is not recognized by the MHD module.
Normal, ' ': Use the standard Roe-averaging of the
enthalpy + kinetic-energy fluxes,
(old, default).
CA1: Average the enthalpy and multiply with the average mass flux.
Average the kinetic energy fluxes as in the standard Roe case.
CA1g: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small fluctuations.
Switch smoothly to the Normal Roe averaging for large non-hydrostatic
pressure fluctuations.
CA1gMps: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small Mach numbers.
Switch smoothly to the Normal Roe averaging
for large Mach numbers or large fluctuations
fluctuations in pressure (directly and after subtracting
the hydrostatic pressure correction) and entropy.
This case is recommended.
CA1M: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small Mach numbers.
Switch smoothly to the Normal Roe averaging for
large Mach numbers.
CA1Ms: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small Mach numbers.
Switch smoothly to the Normal Roe averaging
for large Mach numbers or large entropy fluctuations.
CA1p: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small pressure fluctuations.
Switch smoothly to the Normal Roe averaging for large pressure fluctuations.
CA1s: Use the consistent-advection centering for the average enthalpy flux
as in CA1 for small entropy fluctuations.
Switch smoothly to the Normal Roe averaging for large entropy fluctuations.
CA2: Average the enthalpy plus kinetic energy and multiply with the average mass flux.
CA2g: Use the consistent-advection centering for the average enthalpy plus
kinetic energy flux as in CA2 for small fluctuations.
Switch smoothly to the Normal Roe averaging for large non-hydrostatic
pressure fluctuations.
CA2M: Use the consistent-advection centering for the average enthalpy plus
kinetic energy flux as in CA2 for Mach numbers.
Switch smoothly to the Normal Roe averaging for large Mach numbers.
CA2p: Use the consistent-advection centering for the average enthalpy plus
kinetic energy flux as in CA2 for small pressure fluctuations.
Switch smoothly to the Normal Roe averaging for large pressure fluctuations.
CA2s: Use the consistent-advection centering for the average enthalpy plus
kinetic energy flux as in CA2 for small entropy fluctuations.
Switch smoothly to the Normal Roe averaging for large entropy fluctuations.
CA3: Take the Roe tilde average enthalpy plus kinetic energy and multiply
with the computed mass flux.
This is a more experimental version and not generally recommended.
CA4: Averaging the enthalpy and multiply
with the computed mass flux.
This is a more experimental version and not generally recommended.
CA1 variant for the time being.
However, both CA1 and CA2 work only well for small fluctuations and Mach numbers.
Therefore, one of the modified schemes should be used.
Again, they are rather similar even if the implemented creteria are rather different.
While most of the versions work for ``ordinary'' main-sequence models,
the comparably pooly resolved red-supergiant models (with large entropy step and Mach numbers)
require a combination of the criteria above.
Therefore, CA1gMps is recommended (for all type of models in general).
This parameter is not recognized by the MHD module.
0.0: Deactivation of pressure reduction terms
in waves 3 and "6" in Roe solver
1.0: Activation of pressure reduction terms
in waves 3 and "6" in Roe solver (default)
hdEntropyWaveMode='Normal' which
is not recommended, anymore.
This parameter is not recognized by the MHD module.
0.0: No extra energy diffusion down an entropy gradient (default).
0.2: Small value
1.0: Reasonable value
3.0: Large value
C_hydTdiffLin and C_hydTdiffMach that
act on local temperature minima (see below).
This parameter is not recognized by the MHD module.
0.0: No extra energy diffusion down an entropy gradient (default).
0.2: Small value
0.5: Reasonable value
1.0: Reasonable value
3.0: Large value
C_visPrturb)
of by the new, rather simple option to the Roe solver
to apply additional energy dissipation down a temperature gradient but only
in cells adjacent to a local temperature minimum (in 1D). It works
nicely for the Sedov blast wave and does not have any visible adverse impact
in any other cases, so far. I don't expect it to do any harm for
convection simulations and recommend to activate it per default.
Cautious people might not like it and see how well it works without,
though. Still, unlike the tensor viscosity with turbulent Prandtl number
there is no viscous flux down the subphotospheric temperature or
entropy gradient (unless there is a local minimum at the bottom).
The linear diffusion can be set e.g. with
C_hydTdiffMach (see below) has an additional factor,
that takes velocity gradients into account,
which prevent this type of diffusion from acting in deeper convective layers.
I recommend as a default C_hydTdiffLin=0.0 and non-zero values only in case
of an emergency and C_hydTdiffMach=1.0 or 2.0 as a default.
These parameters are not recognized by the MHD module.
c_hydtdifflin,
an additional energy dissipation down a temperature gradient but only
in cells adjacent to a local temperature minimum (in 1D) can be applied,
that has a scaling factor derived from the Mach number.
This Mach-number-dependent diffusion can be set e.g. with
C_hydTdiffLin=0.0 and non-zero values only in case
of an emergency and C_hydTdiffMach=1.0 or 2.0 as a default.
These parameters are not recognized by the MHD module.