Extrude

An extrusion is a 2D geometric description of a model, which can be extruded in the third dimension to create FLAC3D zones. Multiple sets of extrusion data can be created, each under a different name. At any time there may only be one currently active set. All commands on set objects (blocks, points, edges, segments) will apply to the objects in the currently active set only (see extrude set select).

Points are created in space, connected to edges, which are themselves connected into blocks. Edges are either linear or curved, in which case they follow a path given by a number of control points. Blocks of two types can be created in the Extruder: 3- or 4-sided blocks with structured mesh (“regular blocks”) and blocks with 5 or more sides and unstructured mesh (“irregular blocks” - these blocks may have convex or concave boundary, may be multiply-connected and/or contain nested blocks). Both structured and unstructured meshes consist of triangular and/or quadrilateral elements. Upon extrusion, a single zone (brick or wedge) is created from each element of the mesh.

Number of zones and their ratio can be assigned for every edge and they propagate automatically across all regular blocks attached to the edge. However, these parameters are unique for every edge in an irregular block; upon any changes of the edge parameters, including vertex locations, the unstructured mesh has to be re-created. A multiplier factor can be assigned to a regular block to increase (densify) the number of zones in it. Irregular blocks do not use multipliers.

Points, edges, and blocks can be assigned group names, which are then assigned to the gridpoints, faces and zones derived from them.

The extrusion data are also accessible by FISH, which means that an extruded geometry can be scripted and parameterized.

The Extrusion Pane of the FLAC3D interface provides graphical input of these commands. As one performs operations in the Extrusion pane to build a set, the commands underlying those operations — as detailed here — are emitted in the record and will be saved with the model state in a save (*.sav or *.f3dsav) file. The information in this section is a reference on the extrusion commands and FISH functions. See The Extrusion Pane for instructions on constructing extrusions graphically in the interface.