Course stability analysis for towing system of a gravity-based structure in managed ice fields

ABSTRACT

Compared to open water, the presence of ice floes in ice-covered water may pose additional challenges to the towing operations of offshore platforms. This paper proposes a numerical model for analyzing course stability of a gravity-based structure during towing operation in managed ice fields, considering coupled motions of tugs, towed platform, and ice floes. A discrete element method is applied to simulate interaction between drifting ice floes and structures, and verified by existing model tests. The motions of tug and towed platform are coupled through a catenary towline model. A proportional-differential controller is employed to adjust heading and lateral position of tug. The effects of main factors, such as tugs’ number, towline length, ice concentration, rudder area and controller gains on course stability are discussed through numerical case studies. The presented numerical approach is expected to provide practical guidance for towing design, and ensure safety of towing operation.

KEYWORDS:

• Towing system
• course stability
• discrete element method
• managed ice
• proportional-differential control

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by National Natural Science Foundation of China [Grant Numbers 51809124, 5181102016, 52171259].