Line Clashing |
 
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Line Clashing |
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Flexcom incorporates a facility for modelling contact between adjacent lines. Typical applications would include the interference that occurs between flexible risers and vessel mooring lines on a floating production system, or between rigid drilling and production risers on a TLP. You create models of the various structures in the normal fashion, and then indicate regions on both structures over which interference is thought likely to occur. The contact algorithm itself is relatively sophisticated – the following aspects in particular are noteworthy:
•The finite element mesh in the contact region need not be particularly refined. Contact is predicted based on the shortest distance between potential contact elements, regardless of the actual element lengths used. This allows contact regions to be initially identified using a relatively coarse model, while the structural response may be more accurately modelled after subsequent mesh refinement.
•Clashing is a complex and highly non-linear phenomenon, so the use of relatively small time steps is essential in order to accurately capture the impact and subsequent structural response. Flexcom continually monitors the relative velocity of approaching lines, allowing the time step to be gradually reduced in anticipation of contact. Once the lines have separated after impact, the time step begins to increase again. This approach facilitates a robust and accurate contact model, while also ensuring an efficient simulation overall.
Further information on this topic is contained in the following sections:
•Contact Stiffness and Damping
•*CLASHING is used to specify regions where clashing may occur, and suitable contact stiffness and damping values.
•*CLASHING SOLUTION is used to specify solution parameters associated with clashing.
•*LINES is used to define a line (and sections within that line), by specifying relevant set names, lengths, start and end locations, and mesh generation settings.
•*TIME is used to define time parameters for an analysis.
If you would like to see an example of how these keywords are used in practice, refer to G01 - Jumper Clashing or J01 - Dropped Object.