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Nodes |
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Nodal locations may be specified in any of the following ways in Flexcom:
i.Directly in terms of global coordinates (using the *NODE keyword)
ii.Generated along a straight line between existing nodes (using the *NODE keyword)
iii.Directly in terms of distance along a cable (using the *NODE,CURVILINEAR keyword)
iv.Generated along a cable (using the *NODE,CURVILINEAR keyword)
v.Automatically created at the start or end point of a line (using the *LINES keyword)
vi.Automatically created during line meshing (using the *LINES keyword)
vii.Automatically positioned at a designated location in terms of distance along a line (using the *LINE LOCATIONS keyword)
Methods (iii) and (iv) relate to the use of cables, and are discussed later in Cables. The use of cables has to a large extent been superseded by the Lines capability, so you can effectively disregard these options as being obsolete. Additionally, generation of straight lines is also possible with lines, so you can ignore method (ii) also.
Methods (v) to (vii) relate to the line generation facility, and are discussed later in Lines.
Hence, method (i) assumes the primary focus of this article.
The specification of nodal locations in terms of global coordinates is self-explanatory. For this option, you define the node directly in terms of a node number and global coordinates. The Flexcom global coordinate system is shown below. Note that the global X axis is vertical in Flexcom. Explicitly defined nodes are useful when modelling structures which do not constitute long slender bodies such as risers and mooring lines. For example, you may wish to model a Floating Body using an arbitrary assemblage of rigid massless beam elements, in which case Nodes and Elements would typically represent the quickest approach.
Global Cartesian Coordinate System
You can also specify nodes as being equally spaced along a straight line joining two nodes. This corresponds to method (ii) above. For this option, you specify the numbers of the end nodes. These end nodes must themselves be defined directly, or in a separate generation. You can also optionally specify the increment to be used in assigning node numbers to generated nodes, or simply let the program use the default value of 1.
When nodes are automatically generated from Lines, you do not concern yourself with explicit node and element numbering. The meshing process is similar to what you could achieve manually, but without all the unnecessary hassle.
Note that Flexcom automatically performs bandwidth optimisation to reduce the bandwidth of the system matrices if possible. This means that any arbitrary node numbering scheme may be used without adversely affecting the speed of execution of a particular Flexcom analysis.
