26/08/2020
using finite element analysis to decrease risk and increase success
Single vessel tow
Icebergs pose risks to oil and gas development offshore eastern Canada: in case of impact/interaction, facilities could be damaged; in response to possible impact, personnel could be evacuated and production shut down. One of the most effective ways of mitigating these risks of damage or downtime, demonstrated throughout 20+ years of producing operations on the Grand Banks, is to tow encroaching icebergs away from facilities using a boat and tow cables or nets. However, the physics involved are complicated and can be tricky. Both the tow vessel and the iceberg are in motion – drifting and bobbing with currents, waves and wind. Also, icebergs are both IN and MADE OF water, so they are inherently slippery; tow cables or nets can slip over or under the berg, perhaps causing it to roll and requiring a repeat of the “lasso” operation.
C-CORE is working to improve iceberg management through a system that integrates real-time capture of 3D iceberg profiles (both above and beneath the waterline) with a 3D dynamic model that can simulate iceberg towing operations in advance. This system will show the best way to tow a particular iceberg, simplifying and speeding up the process.
Modelled tow showing final net position
The 3D towing model applies the ‘Total Lagrangian’ Finite-Element Method to model the cable-and-rope structure between the tow vessel and the iceberg, as well as a contact model that includes sticking and sliding friction between the rope/net and iceberg. This towing model can therefore account for cable deformities and different kinds of friction. Future iterations of this model will introduce simulation of iceberg motion, wind and wave forces, and automatic local cable re-meshing. It will also have a graphical user interface. This model will be incorporated into the Smart Ice Management System (SIMS), which has been under development at C-CORE since 2015.
NOTE: A technical paper on development of this 3D dynamic iceberg towing model was published at OMAE2020:
O’Rourke, B.J., Fuglem, M.K., King, T. (2020). 3-D Simulation of Iceberg Towing Operations: Cable Modeling and Frictional Contact Formulation using Finite Element Analysis (OMAE2020-18788). Proceedings of the ASME 39th International Conference on Ocean, Offshore and Arctic Engineering OMAE2020, August 3-7, Virtual.