GEOMETRY BODY Control

        

This command is used to define new bodies or to redefine existing bodies. FEMGEN bodies may have either a fixed or flexible topology.

FEMGEN bodies with flexible topology may be generated using either a PRISM or a GENERAL BODY. A PRISM may be created automatically when the GEOMETRY SWEEP command is used to sweep a region. The topology of the PRISM body is essentially the same as that of the underlying region. A GENERAL BODY is created from a set (or sets) containing a number of bounding surfaces. A GENERAL BODY may have a topology that is considerably more flexible than that of the PRISM.

If adjacent geometric parts are created separately and have an identical mesh on the boundary, then in order to join them, it may be necessary to use the MESHING MERGE command to ensure that the final mesh is continuous across the boundary.

FEMGEN bodies with fixed topology have four, five or six sides. These sides may be specified explicitly, or for five and six sided bodies implicitly by specifying two opposing surfaces and allowing FEMGEN to automatically generate the connecting sides.

When five or six sided bodies are being created the full definition requires two surfaces that are opposite one another, followed by the remaining surfaces in sequence. There is a shortened definition using just two opposing surfaces; when this is used FEMGEN will generate the least twisted body that can be created from the specified surfaces, although if this definition is not the one required then the full definition of the body must be given.

For tetrahedral bodies all four surfaces must be specified.

Bodies may also be generated automatically when the GEOMETRY SWEEP command is used to sweep one or more surfaces.

The sub-commands ELEMENTS, 2SURFS, 4SURFS, 5SURFS, and 6SURFS are optional. The command processor is able to determine which option is required from the additional parameters which follow. Once a body has been defined using one of these commands, the command processor assumes that further bodies are to be entered and remains at the GEOMETRY BODY level. From this level, further bodies may be defined or a different primary command may be selected.

GEOMETRY BODY has the following sub-commands:

2.8.1.1 GEOMETRY BODY ELEMENTS - From a set of elements

2.8.1.2 GEOMETRY BODY SETS - From two sets of topologically equivalent surfaces

2.8.1.3 GEOMETRY BODY 2SURFS - Two-sided definition

2.8.1.5 GEOMETRY BODY 4SURFS - Four-sided definition

2.8.1.5 GEOMETRY BODY 5SURFS - Five-sided definition

2.8.1.6 GEOMETRY BODY 6SURFS - Six-sided definition

2.8.1.7 GEOMETRY BODY GENERAL - Multiple-sdied definition from bounding sets

2.8.1.8 GEOMETRY BODY PRISM - Multiple-sided definition from a region

sec:geometry:body:general

Notes:

1.

In-line editing of body definitions
The commands GEOMETRY body_name /EDIT and GEOMETRY /PICK-B /EDIT will cause up to 80 characters from the definition of the specified or picked body to be loaded into the input buffer for in-line editing.