Specifying the extent of the physical domain

CoordBase provides a way for specifying the extent of the simulation domain that is independent of the actual coordinate and symmetry thorns. This is necessary because the size of the physical domain is not necessarily the same as the size of the computational grid, which is usually enlarged by symmetry zones and/or boundary zones.

The physical domain is characterised by the location of its lower and upper boundary and by its grid spacing. These quantities are related to the extent and the number of grid cells that span the domain. The relation between the size of the domain and the size of the computational grid is defined in section A3.9 below. The domain extent as defined in this section is the continuum extent and is independent of the actual discretisation. This makes it possible to adapt the same domain specification for different resolutions by changing only a single parameter.

The domain is specified in one of the following ways, which is selected by the keyword parameter domainsize:

minmax:

by the location of its lower and upper boundary

extent:

by its extent, i.e. its width

spacing:

by grid spacing and the number of grid cells

The domain specification uses the number of grid cells instead of the number of grid points because the latter can easily lead to one-off errors.

The domain size in each dimension is specificied in equivalent ways. For example, the $x$-dimension is specified by a set of some of the following parameters:

zero_origin_x (boolean):

When the domain size is specified by extent or by spacing, then the origin (lower boundary) can either be located at $x=0$, which leads to the domain $x \in [0,L]$ with the extent $L$, or the domain can be symmetric with respect to $x=0$, which leads to $x \in [-L/2,L/2]$.

xmin and xmax:

When the domain is specified by the location of its lower and upper boundary, then these specify the locations.

xextent:

When the domain is specified by its extent, then this specifies the extent.

dx (real) and ncells_x (int):

When the domain is specified by grid spacing and the number of grid cells, then these specify the grid spacing and the number of grid cells.