Mask
An excision region enables the user to remove a singularity from the
computational domain. This idea is used most in numerical relativity simulations
evolving black holes, where the singularity is excised via a mask function. The parameters
controlling the mask usage are:
- use_mask = 0 [default] No mask is used in the simulation.
= 1 A mask may be needed during a simulation.
- mask_period : this parameter indicates how many fine mesh steps are taken
between masking. [default = 1]
- mask_usemin = 0 [default] turns off the initialization of the horizon finder
using the minimum of a user specified gridfunction and instead uses user inputs on the location
of the mask.
= 1 turns on initialization of the horizon finder using the
minimum of a user designated field (mask_minfield).
- mask_minfield = 1 [default] Number of the field to minimize ( see fields.inc
to related field number to field name )
- mask_type : this parameter is deprecated. In earlier versions, HAD supported
both spherical and cubical excision regions. It now only supports cubical excision regions.
The size of the mask and the location of the mask is tied to the apparent horizon finder.
Notes
- The maximum number of independent excisions supported is two.
- The mask has it's own grid function, mask. This can be output
into an sdf file by setting output_mask = 1. It has a value less than zero at
excised points and greater than zero elsewhere.
- If findhorizon = 1, the driver will determine the appropriate mask size
for the excision region. See apparent horizon finder.
- If findhorizon = 0, the user can directly control the mask size and location
through the mask_center and mask_radius arrays defined in had/include/mask.inc.
See Also
apparent horizon finder
Index of all manual pages
Examples
None