region command¶
Syntax:¶
region ID style args keyword value ...
ID = user-assigned name for the region
style =
blockorcylinderorplaneorsphereorunionorintersect- block args = xlo xhi ylo yhi zlo zhi
- xlo,xhi,ylo,yhi,zlo,zhi = bounds of block in all dimensions (distance units)
- cylinder args = dim c1 c2 radius lo hi
- dim = x or y or z = axis of cylinder
- c1,c2 = coords of cylinder axis in other 2 dimensions (distance units)
- radius = cylinder radius (distance units)
- lo,hi = bounds of cylinder in dim (distance units)
- plane args = px py pz nx ny nz
- px,py,pz = point on the plane (distance units)
- nx,ny,nz = direction normal to plane (distance units)
- sphere args = x y z radius
- x,y,z = center of sphere (distance units)
- radius = radius of sphere (distance units)
- union args = N reg-ID1 reg-ID2 …
- N = # of regions to follow, must be 2 or greater
- reg-ID1,reg-ID2, … = IDs of regions to join together
- intersect args = N reg-ID1 reg-ID2 …
- N = # of regions to follow, must be 2 or greater
- reg-ID1,reg-ID2, … = IDs of regions to intersect
zero or more keyword/value pairs may be appended
keyword =
side- side value = in or out
- in = the region is inside the specified geometry
- out = the region is outside the specified geometry
Examples:¶
region 1 block -3.0 5.0 INF 10.0 INF INF
region 2 sphere 0.0 0.0 0.0 5 side out
region void cylinder y 2 3 5 -5.0 INF
region outside union 4 side1 side2 side3 side4
region slab plane 0.2 0 0 1 0 0
Description:¶
This command defines a geometric region of space. Various other commands use regions. See the group grid, group surf, and dump_modify commands for examples.
Commands which use regions typically test whether a point is contained
in the region or not. For this purpose, coordinates exactly on the
region boundary are considered to be interior to the region. This means,
for example, for a spherical region, a point on the sphere surface would
be part of the region if the sphere were defined with the side in
keyword, but would not be part of the region if it were defined using
the side out keyword. See more details on the side keyword below.
The lo/hi values for the block or cylinder styles can be specified
as INF which means a large negative or positive number (1.0e20).
For style cylinder, the c1,c2 params are coordinates in the 2 other
dimensions besides the cylinder axis dimension. For dim = x, c1/c2 =
y/z; for dim = y, c1/c2 = x/z; for dim = z, c1/c2 = x/y. Thus the third
example above specifies a cylinder with its axis in the y-direction
located at x = 2.0 and z = 3.0, with a radius of 5.0, and extending in
the y-direction from -5.0 to infinity.
For style plane one point and the normal vector define the plane limiting the region. All grids to one side of this plane belong to the region. Which side is determined by the normal and the keyword side. Thus, the fourth example above specifies a region consisting of the semispace located to the right of the point x=0.2 (normal pointing in the direction of +x).
The union style creates a region consisting of the volume of all the
listed regions combined. The intersect style creates a region
consisting of the volume that is common to all the listed regions.
Important
Regions in SPARTA are always 3d geometric objects, regardless of whether the dimension of the simulation 2d or 3d. Thus when using regions in a 2d simulation, for example, you should be careful to define the region so that its intersection with the 2d x-y plane of the simulation has the 2d geometric extent you want.
The side keyword determines whether the region is considered to be
inside or outside of the specified geometry. Using this keyword in
conjunction with union and intersect regions, complex geometries can
be built up. For example, if the interior of two spheres were each
defined as regions, and a union style with side = out was
constructed listing the region-IDs of the 2 spheres, the resulting
region would be all the volume in the simulation box that was outside
both of the spheres.
Restrictions:¶
none
Default:¶
The option default is side = in.