OC4 P1 LC4.3b Deans Wave |
 
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OC4 P1 LC4.3b Deans Wave |
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This load case is very similar to OC4 P1 LC2.3b, which considers a rigid offshore wind turbine rather than a flexible offshore structure. Results are naturally very similar also.
The vertical force at the mudline predicted by Flexcom shows good agreement with the other software tools. As outlined in OC4 P1 LC2.1, the project participants which omitted the buoyancy force at the mudline predict a mean vertical force at about -16600 kN, while others (including Flexcom) which included this term predict a mean vertical force of about -15800 kN. Differences in peak-to-peak amplitude of vertical force are mainly due to the buoyancy calculation method, whether displaced volume or pressure integration. Additionally, different masses for the jacket substructure and marine growth contributed to discrepancies.
Very close agreement is shown between all software tools for the fore-aft shear force at the base of the jacket. Minor discrepancies in peak-to-peak amplitude may be caused by dissimilarities in implementations of wave kinematics, or slight differences originating in the modelling of the support structure. Results from SWE/Flex5-Poseidon appear out of phase with the other tools - a minor fault in the software at that time caused an unexpected phase shift in the output.
The fore-aft shear force at the top of the tower shows considerable variation across the different software products. However the response predicted by Flexcom shows good general agreement with many of the other tools in terms of response amplitude and period.
Popko et al. (2012) note that the out-of-plane displacement in the fore-aft direction, of the central joint of the cross-brace at level 2 on side 2 (see OC4 Jacket schematic for further details), shows a remarkably good agreement across the different software products. Close agreement is also demonstrated by Flexcom. As with the fore-aft shear force at the mudline, results from SWE/Flex5-Poseidon are out of phase with the other tools due to a minor fault in the software that caused an unexpected phase shift in the output.
