Physical Model Tests for Ship Manoeuvring in Ice

Ore carriers navigating through ice filled channels and icebreakers escorting cargo ships are two examples of ships which must manoeuvre in ice. Information about the manoeuvring ability of such ships is required for ship design, for voyage planning, and for personnel training. With numerical simulation the eventual goal, physical model tests are an essential step in determining ship manoeuvring equations and parameters. Simulation of ship manoeuvers in ice must take into account dynamics which are qualitatively different from those which control motions in open water. The constraining ice forces may be an order of magnitude larger than the corresponding hydrodynamic forces, and in fact are usually the limiting factors for ship operations in ice. The usual Fourier methods used to determine hydrodynamic coefficients from open water PMM tests are not appropriate for ice manoeuvering analysis, for several reasons. The form of the manoeuvering equations in ice is different from that in open water. Runs in the ice tank are restricted in length, and the number of runs is restricted by the time and cost to produce an ice sheet. This paper outlines a new methodology for manouvering testing and analysis which takes into account both the complexity of the ship-ice interaction and also the requirement to obtain information in a cost-effective manner.