Protection Options

There are several ways to handle density and pressure protections in AstroBEAR. These parameters can all be set in physics.data

The most two important parameters are:

• MinTemp which sets the threshold for protections of pressure and is in Kelvin
• MinDensity which sets the threshold for protections of density and is in CU (computational units)

Density Protections

• When the density in a cell drops below the MinDensity the code can either restart from the last root step or modify the density and continue. lRestartOnDensityProtections controls this behavior

There are a few ways to modify the density

• Set it to MinDensity (iDensityProtect = 0)
• Set it to the minimum nearby density (iDensityProtect = 1)
• Set it to the average surrounding density (iDensityProtect = 2)

And usually the momentum needs to be modified to avoid high flow speeds.

• Momentum conserving (iMomentumProtect = 0)
• Set to zero (iMomentumProtect = 1)
• Average of nearby velocities (iMomentumProtect = 2)

Pressure Protections

• When the temperature in a cell drops below the MinTemp the code can either restart from the last root step or modify the energy and continue. lRestartOnPressureProtections controls this behavior.

There are a few ways to modify the pressure

• Set the temperature to MinTemp (iPressureProtect = 0)
• Set the pressure to the minimum nearby pressure (iPressureProtect = 1)
• Set the pressure to the average nearby pressure (iPressureProtect = 2)
• Set the temperature to the minimum nearby temperature (iPressureProtect = 3)
• Set the temperature to the average nearby temperature (iPressureProtect = 4)

In general the higher the protection number, the more 'robust' the code will be. So the default mode is

lRestartOnDensityProtections=.false.
lRestartOnPressureProtections=.false.
iDensityProtect=2
iMomentumProtect=2
iPressureProtect=4

Any of these can be modified by adding lines to physics.data.