System Modelling |
 
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System Modelling |
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The riser hang-off at the top of the SCR incorporates an I-tube which is modelled in Flexcom as a single rigid beam. The riser has a natural hang-off angle in the initial position of 12°, but an 18.5° hang-off angle is subsequently achieved via the Solution Criteria Automation feature. The seabed is modelled as flat and elastic, with both longitudinal and transverse friction coefficients specified. The riser is filled with seawater. The figure below shows the SCR layout.
SCR Layout
The seabed touchdown region and at the vessel hang-off are the areas where the SCR response due to vessel motions is most critical. The riser design requires that von Mises and bending stresses cannot exceed allowable values at any point along the SCR. Likewise effective compression must be avoided at all costs. From the point of view of riser modelling, sufficient element refinement at touchdown is important to ensure predicted values in this region are realistic.
The figure below shows the SCR system at hang-off as the FPSO undergoes environmental loading. It is important to closely monitor this region as the vessel motions, which are dictated by the applied environment, can induce large moments and stresses in the SCR at this point.
FPSO under Environmental Loading