Analyses |
 
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Analyses |
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The base of the riser is fixed in all degrees of freedom. The upper ends of the tensioner elements are attached to the vessel. In addition an internal fluid of density 1970kg/m3 is contained in the riser.
The boundary conditions remain unchanged and are carried through automatically from the initial static analysis. A piecewise-linear cross current is also applied to the drilling riser. The direction of the current is constant with depth and is flowing in the positive sense of the global Y-axis.
VIV effects are considered, as a modal analysis of the drilling riser is performed using Modes, and enhanced drag coefficients are computed using Shear7. As not all users will have both programs installed, this portion of the analysis is performed in advance, and the Shear7 output file (Example16-DR-shear.plt) is simply referenced subsequently in the static current analysis of the production riser.
The base of the riser is fixed in all degrees of freedom. The upper ends of the tensioner elements are attached to the vessel. An internal fluid of density 1400 kg/m3 is contained in the riser.
As part of a wake interference analysis which includes VIV effects, Flexcom automatically performs a modal analysis of the downstream structure, and proceeds to perform a Shear7 analysis to compute enhanced drag coefficients.
In order for this to be possible, the modal analysis file must be created in advance so that Flexcom can access it subsequently as part of the wake interference analysis.
In the modal analysis, the riser type is designated as TTR, 100 eigenpairs and 20 modes are requested, and the riser is divided into 80 equally spaced segments for the purposes of generating Shear7 input data.
The boundary conditions remain unchanged and are carried through automatically from the initial static analysis. A piecewise-linear cross current is also applied to the production riser. The direction of the current is constant with depth and is aligned with the global Z-axis.
This analysis is performed twice; ignoring the presence of the drilling riser in the first instance, and then taking wake interference effects into account. It is interesting to quantify the influence of wake interference on the overall configuration of the production riser and consequently its effect on the clearance between the risers.
The clearance between the upstream (drilling) and downstream (production) risers is computed using Clear, the Flexcom postprocessor for clearance/interference calculations. Separate runs are performed for the cases including and excluding wake interference effects.