Equivalent Nodes |
 
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Equivalent Nodes |
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A Flexcom feature that can simplify setting up and refining finite element models is the option of equivalent nodes. This allows you to specify that two individual nodes, which have been previously defined, are in fact the same node from the point of view of the finite element discretisation.
The usefulness of this feature is best illustrated by an example. Suppose we have defined two cables. The node numbers on the first cable run from 1 to 51, while those on the second cable run from 101 to 151. If we wished to join these cables end to end, we could change the node numbering on the first cable to run from 1 to 50, with the last node numbered 101. However this is not very convenient, and destroys the sequential node numbering on the first cable.
Instead, we can simply define that Nodes 51 and 101 are equivalent nodes, that is, we can specify that they are actually the same node. This has the effect of joining the two cables end to end, while preserving the sequential node numbering scheme on both cables. This makes subsequent refinement of the finite element mesh on either cable a much simpler task. Of course, for two nodes to be defined as equivalent, they must have the same nodal coordinates.
The use of equivalent nodes is particularly associated with the line generation facility (which is described in Lines). Individual lines are defined separately in terms of start and end points during the model building process. Where two lines are to be connected together, the relevant points at the intersection (e.g. the end of the first line and the start of the second line) are identified as equivalent, which facilitates the finite element mesh generation.
•*EQUIVALENT is used to specify that two individual nodes are a single equivalent node.
If you would like to see an example of how this keyword is used in practice, refer to Example A01 - Deepwater Drilling Riser.