Coupled dynamics of deepwater structures – issues and challenges

ABSTRACT

Offshore systems consisting of floaters linked to line structures such as risers and mooring lines are favoured for deepwater applications. The dynamic coupling analysis of a floater together with the line structures has been the subject of several studies in recent years. Powerful numerical tools have been developed implementing full-fledged time-domain approaches as well as more efficient frequency-domain approaches for the analysis of deepwater systems. The present article provides a brief overview of coupled analysis techniques employing both time-domain and frequency-domain approaches, focusing on the basic modelling issues and challenges. It is worth formulating compact but sufficiently accurate dynamic models of line structures. The consequence of truncation errors of numerical integration schemes in long-term time-domain simulations needs to be studied. There is a need to standardise the statistical linearisation approach applied to dynamic response which spreads over a very wide frequency range. Verification of the nonlinear drag force model in the Morison equation through basic computational fluid dynamics studies may be undertaken.

KEYWORDS:

• deepwater structures
• floaters
• moorings and risers
• coupled dynamics
• time-domain and frequency-domain approaches

Acknowledgements

The author is grateful to all the reviewers for their valuable suggestions.