Hang-off Modelling Method in Global Simulation of Flexible Risers

YANG Hongbiao

doi:10.7643/issn.1672-9242.2025.06.011

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Equipment Environmental Engineering ›› 2025, Vol. 22 ›› Issue (6) : 93-100. DOI: 10.7643/issn.1672-9242.2025.06.011

Ships and Marine Engineering Equipment

Hang-off Modelling Method in Global Simulation of Flexible Risers

YANG Hongbiao

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Abstract

The work aims to study the effect of hang-off modelling method on the dynamic response and fatigue damage of unbonded flexible risers and provide selection recommendations. Firstly, the attachment and line contact functions in OrcaFlex were used to establish the calculation models for the traditional method (referred to as “ATM method”) and the pipe-in-pipe method (referred to as “PIP method”), respectively. Then, the models were verified to ensure that the results were authentic. Next, the two methods were adopted to analyze some certain flexible riser and the dynamic response and fatigue damage of the riser were compared to identify the difference in results. The maximum curvatures from the ATM method and the PIP method were close under the severe sea state, but exhibited significant difference under the mild sea state. According to the selected sea state, the maximum curvature of the target riser obtained from the PIP method was 7 times that from the ATM method. However, the maximum curvature range from the PIP method was always larger than that from the ATM method, no matter under the severe or mild sea state, and a proportion of more than 20% was observed in the case study. The fatigue damage of the riser was positively correlated with its curvature range. The maximum damage from the PIP method increased by 26.2% compared with that from the ATM method. Given that the ATM method does not always give the results on the conservative side, it is recommended to use the PIP method to model the hang-off region of flexible risers. The use of the PIP method not only predicts the riser response accurately, but also helps the design of bend stiffeners.

Key words

unbonded flexible riser / hang-off region / bend stiffener / curvature / curvature range / fatigue damage

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YANG Hongbiao. Hang-off Modelling Method in Global Simulation of Flexible Risers[J]. Equipment Environmental Engineering. 2025, 22(6): 93-100 https://doi.org/10.7643/issn.1672-9242.2025.06.011

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