Data hierarchy refers to the five types of data (called entities) you will work with during the construction of your grid. Fidelity Pointwise organizes the entities into five types:
The data hierarchy's foundation is the database: a geometry model of the object on and around which a grid is to be generated. You typically obtain the database from a computer aided design (CAD) system and import it into Fidelity Pointwise. Fidelity Pointwise also provides tools for creating database entities. A database can consist of points, curves, surfaces and other topological data like trimmed surfaces. Keep in mind, however, that Fidelity Pointwise does not require a database; the geometry of the grid entities you create may implicitly define the grid's shape. Furthermore, Fidelity Pointwise does not require the database to represent a closed solid model, it can use CAD models with gaps and overlaps in them.
Tip: Because Fidelity Pointwise maintains hierarchical relationships between grid and database entities, it can automate many parts of the grid generation process.
There are three grid entities in Fidelity Pointwise's hierarchy: connectors (curve grids), domains (surface grids), and blocks (volume grids). Grid entities are ordered according to their computational dimension. Note, however, that all of Fidelity Pointwise's grid entities may have a 3D shape (i.e. all three components of the Cartesian coordinates (x,y,z) may vary).
Connectors, the grid entity at the bottom of the hierarchy, are curves on which grid points are distributed. A connector, what a CAD system would call a composite curve, consists of one or more segments. Segments are basic curve types, which can be polylines, polycurves, conics and circles, or curves obtained from a database.
The grid entity in the middle of the hierarchy is the domain, a surface grid. An initial domain grid is generated automatically using a default method when the domain is first created. A variety of grid methods can then be applied to improve the grid's quality.
Volume grids, called blocks, are at the top of the data hierarchy. As with domains, the initial block grid is created automatically, and a variety of grid methods may then be applied to improve the grid's quality.
The last element in Fidelity Pointwise's hierarchy are the source entities. These entities have spacing and decay attributes used to control the local target spacing in connectors (with an Automatic grid point distribution function), domains, and blocks.
This data hierarchy provides the framework by which modifications to any entity are propagated throughout the rest of the hierarchy. For example, modification of a connector's shape will update all domains and blocks that use it. The term "forward editing" refers to grid changes propagated up the hierarchy while "backward editing" refers to downward propagating changes. Fidelity Pointwise's data hierarchy and forward and backward editing allow you to change one entity of your grid and have Fidelity Pointwise make the entire grid system consistent with your change.