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Outer Diameter

For the Flexible Riser format, the outer diameter Do is an appropriate input only if:

•You are using the Distributed buoyancy option, or

•External coatings are specified

In either of these cases Do is a required input, and is taken to represent the actual outer diameter of the riser (without for example buoyancy material).

In terms of buoyancy, Flexcom uses Do to calculate the buoyancy loads generated by the riser itself, and these are summed into the element load matrix in the usual way. The difference between the buoyancy loading calculated using Do, and the buoyancy loading calculated using Db, is then applied as a uniformly distributed load in the element axial direction, as discussed earlier in this section.

If you are using the Default buoyancy option and you have not specified any external coatings, then any value you specify for Do is immaterial and unused. It is because this entry is optional in the majority of cases that the external diameter for the calculation of stresses defaults to Dd when you use the Flexible Riser format.