FLAC3D Mesh Generation

FLAC3D 6.0 ramps up the extension of the mesh generation toolset that was begun with version 5.0  That version added geometry-based meshing with automatic octree generation from surfaces and volumes (left), topography extrusion (center), and 2D extrusions (right). In version 6.0 the new Building Blocks facility provides an easy, interactive means of building structured meshes in 3D, and methods to generate blocks from geometry or to drape blocks on an existing geometry. In addition, the program's import capabilities have been expanded to include ABAQUS and ANSYS meshes.

 

         

Building Blocks

Building Blocks is a built-in interactive mesh-generating facility that is akin to a 3D extruder.  Users may import CAD data (DXF and STL formats) and assemble a series of connected blocks using a powerful yet easy-to-use handle control. The handle serves a variety of functions, acting as a reference point and enabling manipulation (position, scale, rotate, limit) of Building Blocks objects (blocks, faces, edges, and gridpoints). Objects can be snapped to locations, other objects, or imported geometry.  Object points may be merged.   Block refinement operations include splitting, hiding/showing, cutting, copying, and pasting. Building Blocks also permits interactive control of grid ratio and density, edge curvature, automatic block quality checking, and automatic zoning based on: a target zone length, model resolution (extent), or total number of model zones.

Building Blocks works seamlessly with the FLAC3D 6.0 extruder tool and new Model Pane. Building Blocks includes a library of model primitives and users can add and load their own building block sets.

 

 

Structured Meshing

Starting with simple blocks, a final set of blocks can be assembled by snapping block points onto an imported geometry (DXF or STL; see below left). By splitting blocks diagonally a radial mesh can be generated. The mesh is rounded by fitting arcs (or splines), using control points, through polylines. The blocks are then finalized (below, right) using a series of transformation and property settings.

         

Generate from Geometry

The Building Blocks tool incorporates some basic automatic meshing functionality from KUBRIX Geo in a  "Generate From Geometry" command.  

Users may generate building blocks if additional manipulation will be needed, or they may create zones directly from the geometry.  Zones may be either hexahedrons (below left) or tet-split (tetrahedrals split into hexadedrons, below right). Griddle and BlockRanger are available for more advanced mesh generation needs.

 

    

Draping

A new drape command may be used to conform an edge or edges of building blocks to the edges of a surface on an imported geometric data set.  The command will move body points and control points in a specified direction until they meet a polygon in the geometric set. (The geometric set must have polygons, not just lines.)  Adding blocks and control points will affect the resulting resolution of a drape command — a progression of block refinement, from coarse to fine, is shown below.  Additional zones are easily added simply by selecting any vertical edge and increasing the zoning along that edge.

      

Mesh Importing

In addition to Itasca's proprietary grid format, FLAC3D 6.0 can also now import both ABAQUS grid (*.inp) and ANSYS grid node (nlist and elist, *.lis) file formats. Any number of third-party programs generate and use these, which makes them ideal transitional formats between users' custom mesh data and FLAC3D.

An imported ANSYS mesh (left) and ABAQUS mesh (right) can be seen below as FLAC3D 6.0 model zones, colored by groups.

         

BlockRanger Included

BlockRanger is a fully interactive, volume mesh generation plug-in for the Rhinoceros 5.0 3D CAD system.  BlockRanger converts Rhino 5 solids into blocks of high-quality hexahedral (brick) elements for use with most engineering analysis packages that require hexahedral meshing and a strict control of element quality, spatial distribution, and orientation. BlockRanger is included with the purchase of a FLAC3D 6.0 license at no extra cost. A Rhinoceros 5.0 license is required in order to use this free plug-in.