zone create command

Syntax

zone create keyword

Primary keywords:

brick    cylindrical-shell    cylinder    cylindrical-intersection    degenerate-brick    pyramid    radial-brick    radial-cylinder    radial-tunnel    tetrahedron    tunnel-intersection    uniform-wedge    wedge

The zone.create command fills primitive shapes ( brick, cylinder, etc.) with a predefined grid pattern.

See Primitive-Based Grids for further discussion and examples of the process of creating a mesh using primitive shapes.

To create zones from a 2D cross section that is then extruded into a third dimension, see the Extrude section and the i Extrusion pane, along with the command zone generate from-extruder.

To create zones from an interactive assembly of blocks, with control over curved edges, see the Building-Blocks section and the i Building Blocks pane, along with the command zone generate from-building-blocks.

To create individual gridpoints see zone gridpoint create.

Individual zones may be created with this command using the brick keyword and the size set to (1,1,1).

FLAC3D may also read in externally generated grids in several formats, see the zone import command.

On meshing with zone create

• see Primitive-Based Grids in Problem Solving with FLAC3D
• see Further Discussion: Meshing With Primitives in Tutorial: First FLAC3D Model

Note

Thumbnails of primitives are links (may be clicked) to enlargements that indicate the shapes’ reference points.

After each shape keyword is a block of modifiers that control its position, shape, and zone distribution. These are marked [zonecreateoptions] in the commands, with definitions found in the “Keyword Block” section at the end of this topic.

IMPORTANT: image setup below works for CHM output ONLY; clicking a thumbnail in HTML output will result in a “Page can’t be displayed” error. DO NOT TRY TO FIX.

to do: the full size images for the primitives should be redone for html format; the numbers are too hard to read

brick [zonecreateoptions]

hexahedral brick-shaped mesh with eight vertices

cylindrical-shell [zonecreateoptions]

cylindrical shell mesh

cylinder [zonecreateoptions]

cylindrical-shaped mesh

cylindrical-intersection [zonecreateoptions]

Intersection of two cylinders

degenerate-brick [zonecreateoptions]

degenerate brick mesh, with two vertices merged

pyramid [zonecreateoptions]

pyramid-shaped mesh

radial-brick [zonecreateoptions]

radially graded mesh around brick

radial-cylinder [zonecreateoptions]

radially graded mesh around cylindrical-shaped tunnel

radial-tunnel [zonecreateoptions]

radially graded mesh around parallelepiped-shaped tunnel

tetrahedron [zonecreateoptions]

tetrahedral-shaped mesh

tunnel-intersection [zonecreateoptions]

tunnel intersection

uniform-wedge [zonecreateoptions]

uniform wedge-shaped mesh

wedge [zonecreateoptions]

wedge-shaped mesh

Table 14: Summary of Mesh Shape Properties

Name/Keyword	Reference Points	Size Entries	Dimension Entries	Fill
brick	8	3	0	no
degenerate-brick	7	3	0	no
wedge	6	3	0	no
uniform-wedge	6	3	0	no
pyramid	5	3	0	no
tetrahedron	4	3	0	no
cylinder	6	3	0	no
radial-brick	15	4	3	yes
radial-tunnel	14	4	4	yes
radial-cylinder	12	4	4	yes
cylindrical-shell	10	4	4	yes
tunnel-intersection	17	5	7	yes

Keyword Block

Zone Create Modifiers

The characteristics of the created shape (e.g., global coordinate positions, number of zones) are defined by specifying the keywords given below, after the shape keyword. The numerical entries associated with each shape are summarized in the table above and illustrated in the figures (click any thumbnail image above for a reference enlargement). The shape keywords of zone.create shown above will accept the keywords listed in the block below, except where noted otherwise in the descriptions. The major keywords are: brick, cylinder, cylindrical-intersection, cylindrical-shell, degenerate-brick, pyramid, radial-brick, radial-cylinder, radial-tunnel, tetrahedron, tunnel-intersection, uniform-wedge and wedge.

dimension f ...

Specify the dimensions of interior regions for some shapes. These are used if the control point is not specifically given. Up to seven dimension entries may be required for a shape (f1, f2, f3, … , f7). Refer to the figures above for entries and dimensions. If dimension is not given the entries are calculated as 20% of the lengths between reference points.

This keyword can only be used with the following keywords of the zone create command: cylindrical-intersection, cylindrical-shell, radial-brick, radial-cylinder, radial-tunnel, and tunnel-intersection.

edge f

Specify an edge length for the sides of the mesh. If point 1, point 2, and point 3 are not specified, then the magnitude of the distance from point 0 will be defined by edge. By default the edge length is the number of zones specified in that direction.

fill <group s1 <slot s2 >>

If specified, the interior region for some shapes (see Summary of Mesh Shape Properties above) will be filled with zones. If not specified, the interior region will not contain zones. If the optional group keyword is given with a valid name, the name s1 is assigned to the filled zones.

This keyword can only be used with the following keywords of the zone create command: cylindrical-intersection, radial-brick, radial-cylinder, radial-tunnel, and tunnel-intersection.

group s1 <slot s2 >

Assign a group name s1 to this primitive at creation. By default (when the slot keyword is not supplied), the group is assigned to slot Default. Use of the group logic is described in Group.

merge b

Gridpoints on the outer faces of the mesh are merged with existing mesh faces if this keyword is set true. During execution of a zone.create command, a check is made for each boundary gridpoint against the boundary gridpoints of zones that already exist. Internal gridpoints are not checked. If two boundary gridpoints fall within a tolerance of 1 × 10-7 (relative to the magnitude of the gridpoints’ position vector) of each other, they are assumed to be the same point, and the first gridpoint is used instead of creating new ones for all subsequent calculations. If merge is set false, two gridpoints are not merged into one.

point i keyword

The keywords point 0, point 1, point 2 … point 16 specify the reference (corner) points of shapes. By default, point 0 is located at (x = 0, y = 0, z = 0). By default, point 1, point 2, and point 3 are set to the orthogonal distances in the x-, y- and z-directions, with a magnitude equal to the number of zones in that direction. When specifying point 1, point 2, and point 3, the vectors point 0 - point 1, point 0 - point 2, and point 0 - point 3 must form a right-handed coordinate system.

Up to 16 points may be required for a shape. The number required is shown in Summary of Mesh Shape Properties above. The locations of these points are illustrated in the reference images (click on any thumbnail above to access).

The following options are available to define the location of any given point

v <add>

The position is given as a vector v. If the optional keyword add is used, the value of v will be added to the position of point 0.

gridpoint s

The position of the gridpoint with name s is used. See the zone gridpoint create command. This allows to user to create named reference points in space ahead of time, and refer to them when creating primitives.

ratio f1 <f2... >

This specifies a ratio that is used to space zones with an increasing or decreasing geometric ratio. This ratio is defined as creating a zone size distribution such that each zone along the edge is f times the previous. Up to five ratio entries (f5) may be needed for some shapes. For each shape, the entries and their associated zone directions are shown in the reference images (click any thumbnail above). If ratio is not given, all entries default to 1.0.

size i1 <i2 ... >

This specifies the number of zones for each shape. Up to five (i5) may be needed for some shapes. The number required is listed in Summary of Mesh Shape Properties above. The entries and their corresponding directions for each shape are shown in the reference images (click any thumbnail above). If not specified, size values default to 10.

sweep-axis

When this keyword is given, edge point 0 - point 2 is used as an axis about which edges point 1 - point 4 and point 3 - point 5 are swept. Without this keyword, the grid faces fall on the (point 0,point 1,point 3) and (point 2,point 4,point 5) planes.