Start and End Locations

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Start and End Locations

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Start and end locations for lines are defined directly in terms of global coordinates. Definition of these location points is quite similar to the explicit definition of finite element nodes discussed previously, with the exception that the nodes are assigned descriptive names rather than node numbers. It is important to associate meaningful names with line start and end locations, as these names will be used by the program to automatically create relevant node and element labels. For example, you can subsequently reference these node labels when you are applying boundary conditions to your model. This aspect is discussed in more detail shortly, and in the ‘Boundary Conditions’ section later.

Referring again to the Steep Wave Riser example, you would define two location points to define the start and end points of the “Riser” line. The coordinates of these locations would correspond to the original cable end nodes (i.e. Nodes 1 and 71) in the example. The location points would have associated names such as “Riser Start” and “Riser End”, respectively.

The significance of these names is that Flexcom will assign a node label with each name to the nodes that it generates at these locations during mesh generation. Thereafter you can specify, for example, a boundary condition at a location although you have no idea of the actual number of the node there. This is very powerful, and means that you can change minimum and maximum element lengths without, say, any boundary condition or point load data being lost or having to be redefined.

Element labels are also automatically created to identify the first and last elements of each line (and subsection of each line if appropriate) in your model. This feature is particularly useful during postprocessing – for example, you could monitor effective tension at the end of a line without having knowledge of the actual element numbers used in the finite element mesh. In the case of the steep wave riser example, Flexcom will automatically create element labels called “Lower Catenary_First”, “Lower Catenary_Last”, “Buoyant Section_First” etc. and associate these labels with the relevant elements in the finite element mesh.