CORDUROY(4fe) Finite Element Package CORDUROY(4fe)
NAME
corduroy - element mesh generation description file format
DESCRIPTION
The corduroy(4fe) file format is used by the corduroy(1fe)
application for describing the desired element mesh gener-
ation. In general white space is unimportant in a file,
arbitrary numeric expressions may be used, and case of
keywords is unimportant. As per standard convention,
boldface items represent keywords, italicized items repre-
sent the syntax of the grammar, and items in brackets are
optional. The file syntax is shown below.
[ initialization ]
[ generators ]
end
Initialization
The initialization section occurs first in the file if
present. It defines parameters common to all generators
and has the following syntax.
start-node = expression
start-element = expression
constraint = name
material = name
The default start-node and start-element is one. If a
constraint is given then the name will be assigned to the
generated nodes. Similarly, if a material is given then
the name will be assigned to the generated elements.
Generators
The generators section contains specifications for gener-
ating the elements and the associated nodes. The section
has the following syntax.
[ line-generator ]
[ grid-generator ]
[ quadrilateral-grid-generator ]
[ brick-grid-generator ]
[ triangular-mesh-generator ]
Lines
A line-generator specifies the generation of elements
along a line in three dimensions. The generator has the
following syntax.
[ start = triple ]
[ end = triple ]
[ number = expression ]
[ rule = linear | log ]
[ element-type = name ]
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where a triple has one of the following forms:
( expression , expression , expression )
( expression , expression )
If the z-coordinate of a triple is not specified then the
previously specified z-coordinate is used. The initial
default z-coordinate is zero. The start and end triples
define the starting and ending coordinates of the line
respectively. The number of elements along the line is
specified by number. The rule assignment controls whether
the elements are linearly or logarithmically distributed
along the line. The element-type specifies the type of
elements to be generated. The type of the element defined
by name must be a linear element.
Grids
A grid-generator specifies the generation of elements
within a three-dimensional grid. The generator has the
following syntax.
[ start = triple ]
[ end = triple ]
[ x-number = expression ]
[ y-number = expression ]
[ z-number = expression ]
[ x-rule = linear | log ]
[ y-rule = linear | log ]
[ z-rule = linear | log ]
[ element-type = name ]
The start and end triples define the diagonally opposite
corners of the grid. The x-number, y-number, and z-number
assignments specify the number of elements along the x, y,
and z dimensions respectively. Similarly, the x-rule, y-
rule, and z-rule assignments specify whether the elements
are to be generated linearly or logarithmically along the
x, y, and z dimensions respectively. The type of the ele-
ment specified by name must be a linear element.
Quadrilateral Grids
A quadrilateral-grid-generator specifies the generation of
four-node planar elements within a two-dimensional grid.
The generator has the following syntax.
[ start = pair ]
[ end = pair ]
[ x-number = expression ]
[ y-number = expression ]
[ x-rule = linear | log ]
[ y-rule = linear | log ]
[ element-type = name ]
The start and end pairs define the diagonally opposite
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corners of the grid. The x-number, and y-number assign-
ments specify the number of elements along the x and y
dimensions respectively. Similarly, the x-rule, and y-
rule assignments specify whether the elements are to be
generated linearly or logarithmically along the x and y
dimensions, respectively. The type of the element speci-
fied by name must be a four-node planar element.
Brick Grids
A brick-grid-generator specifies the generation of solid
brick elements within a three-dimensional grid. The gen-
erator has the following syntax.
[ start = triple ]
[ end = triple ]
[ x-number = expression ]
[ y-number = expression ]
[ z-number = expression ]
[ x-rule = linear | log ]
[ y-rule = linear | log ]
[ z-rule = linear | log ]
[ element-type = name ]
The start and end triples define the diagonally opposite
corners of the grid. The x-number, y-number, and z-number
assignments specify the number of elements along the x, y,
and z dimensions respectively. Similarly, the x-rule, y-
rule, and z-rule assignments specify whether the elements
are to be generated linearly or logarithmically along the
x, y, and z dimensions respectively. The type of the ele-
ment specified by name must be an eight node solid ele-
ment.
Triangular meshes
A triangular-mesh-generator specifies the generation of
triangular elements within a two-dimensional mesh. The
generator has the following syntax.
[ tolin = expression ]
[ angspc = expression ]
[ angtol = expression ]
[ dmin = expression ]
[ kappa = expression ]
[ min = expression ]
[ max = expression ]
[ boundary = [ pair-list ] ]
[ hole = [ pair-list ] ]
[ element-type = name ]
where a pair has the following form:
( expression , expression )
The tolin, angspc, angtol, dmin, kappa, min, and max
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parameters control the specifics of the mesh generation
and are discussed in the user's guide. The element type
specified by name must be a planar, triangular element.
The boundary assignment specifies the boundary points of
the mesh which must be given in counter-clockwise order.
The pair-list is a sequence of pairs. A hole assignment
specifies a hole within the mesh and similarly the points
must be given in counter-clockwise order. Unlike other
assignments, a hole assignment does not overwrite a previ-
ous assignment but instead adds to it. Thus, more than
hole can be specified by repeating the hole assignment as
many times as necessary.
AUTHOR
The corduroy file format was developed by Jason I. Gobat
(jgobat@mit.edu) and Darren C. Atkinson (atkin-
son@ucsd.edu).
SEE ALSO
corduroy(1fe), felt(4fe).
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