The analysis was then re-run for a 100s duration, with the simulation starting at l east 50s before the extreme amplitude time occurrence, using a static model of the complete subsea installation scenario. The study involved running a 3-hour simulation to determine the time at which each extreme amplitude occurs for a range of wave heading/period combinations, using a static model containing just the installation vessel. As such, a study was performed using OrcaFlex to determine which method correlates most with the worst-case loading for subsea structure and pipeline installation. Knowing which method will capture the worst-case loading and associated limited sea states is critical in the analysis. 100s) that incorporates the expected worst-case loading during a 3-hour simulation at the point of interest on the vessel, such as crane tip or tensioner exit.Ī short simulation can be defined by the largest rise/ fall of a wave or extreme vessel resp onse (max/min heave, velocity or acceleration). Therefore, it is common practice to analyse a short simulation period (e.g. However, this is very computationally expensive to perform due to the large quantity of load cases required. For irregular wave analysis, DNVGL-RP-N103 recommends performing a 3-hour simulation to ensure adequate statistics. Time-domain irregular wave dynamic analysis is performed using OrcaFlex as this is representative of a real sea state as opposed to regular wave. Therefore, it is important to select the correct analysis method to obtain the most accurate results.
When installing subsea structures and pipelines, the ability to capture the worst case loading and limiting sea states during the installation analysis can improve safety offshore and l ower the operational risks.
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