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 generation. 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 represent 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 generating 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 ]

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 element 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 corners of the grid. The x-number, and y-number assignments 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 specified 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 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 element specified by name must be an eight node solid element.

  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 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 previous 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 (atkinson@ucsd.edu).

SEE ALSO
corduroy(1fe), felt(4fe).