**NAME**

corduroy - element mesh generation description file format

**DESCRIPTION**

Thecorduroy(4fe) file format is used by thecorduroy(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]endInitializationTheinitializationsection occurs first in the file if present. It defines parameters common to all generators and has the following syntax.start-node=expressionstart-element=expressionconstraint=namematerial=nameThe defaultstart-nodeandstart-elementis one. If aconstraintis given then thenamewill be assigned to the generated nodes. Similarly, if amaterialis given then thenamewill be assigned to the generated elements.GeneratorsThegeneratorssection 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]LinesAline-generatorspecifies 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 atriplehas 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. Thestartandendtriples define the starting and ending coordinates of the line respectively. The number of elements along the line is specified bynumber. Theruleassignment controls whether the elements are linearly or logarithmically distributed along the line. Theelement-typespecifies the type of elements to be generated. The type of the element defined bynamemust be a linear element.GridsAgrid-generatorspecifies 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] Thestartandendtriples define the diagonally opposite corners of the grid. Thex-number,y-number, andz-numberassignments specify the number of elements along the x, y, and z dimensions respectively. Similarly, thex-rule,y-rule, andz-ruleassignments 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 bynamemust be a linear element.QuadrilateralGridsAquadrilateral-grid-generatorspecifies 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] Thestartandendpairs define the diagonally opposite corners of the grid. Thex-number, andy-numberassignments specify the number of elements along the x and y dimensions respectively. Similarly, thex-rule, andy-ruleassignments specify whether the elements are to be generated linearly or logarithmically along the x and y dimensions, respectively. The type of the element specified bynamemust be a four-node planar element.BrickGridsAbrick-grid-generatorspecifies 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] Thestartandendtriples define the diagonally opposite corners of the grid. Thex-number,y-number, andz-numberassignments specify the number of elements along the x, y, and z dimensions respectively. Similarly, thex-rule,y-rule, andz-ruleassignments 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 bynamemust be an eight node solid element.TriangularmeshesAtriangular-mesh-generatorspecifies 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 apairhas the following form:(expression,expression)Thetolin,angspc,angtol,dmin,kappa,min, andmaxparameters control the specifics of the mesh generation and are discussed in the userâ€™s guide. The element type specified bynamemust be a planar, triangular element. Theboundaryassignment specifies the boundary points of the mesh which must be given in counter-clockwise order. Thepair-listis a sequence ofpairs. Aholeassignment specifies a hole within the mesh and similarly the points must be given in counter-clockwise order. Unlike other assignments, aholeassignment does not overwrite a previous assignment but instead adds to it. Thus, more than hole can be specified by repeating theholeassignment as many times as necessary.

**AUTHOR**

Thecorduroyfile format was developed by Jason I. Gobat (jgobat@mit.edu) and Darren C. Atkinson (atkinson@ucsd.edu).

**SEE** **ALSO**

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